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At least 127 records · Page 7Linked to original sources
PubMed2003

Validation of the USDA/ARS package rinse method for recovery of Listeria monocytogenes from naturally contaminated, commercially prepared frankfurters.

The utility of the U.S. Department of Agriculture/Agricultural Research Service (USDA/ARS) package rinse method for recovering Listeria monocytogenes from the surface of contaminated foods was validated in comparison to the standard USDA/Food Safety and Inspection Service (FSIS) product composite enrichment method and two other methods using frankfurters from a lot with a known package prevalence rate of approximately 16% for this pathogen. One hundred packages from this batch of naturally contaminated, commercially prepared frankfurters were examined as follows: (i) the package exudative fluid was removed and tested using the standard USDA/FSIS product composite enrichment method; (ii) approximately 5 to 7 portions of frankfurters were removed to obtain a 25-g composite of meat that was then processed using the standard USDA/FSIS product composite enrichment method: (iii) 50 ml of 0.1% peptone water was added to each package, and the USDA/ARS package rinse method was performed on the remaining contents; and (iv) after removing the rinse fluid, the solid contents remaining in each package were directly enriched using the USDA/FSIS product composite enrichment method. These four methods identified that 7, 6, 15, and 9 of the 100 packages tested positive for the pathogen, respectively. Although no single approach yielded a positive result for every package that tested positive for L. monocytogenes by any one of the four sampling strategies, the USDA/ARS package rinse method was appreciably (P < 0.05) better than either the package exudate enrichment method or the standard USDA/FSIS product composite enrichment method at recovering the bacterium. These findings validate the sensitivity and ease of use of the USDA/ARS package rinse method using naturally contaminated frankfurters and argue strongly for its adoption for routine screening of ready-to-eat products that are prone to surface contamination with undesirable microbes such as L. monocytogenes.

Animals↗
PubMed2005

Prevalence of Campylobacter, Salmonella, and Escherichia coli on the external packaging of raw meat.

During September and October 2002, 3,662 prepackaged raw meat samples were collected to evaluate the extent and nature of microbiological contamination on external surfaces of the packaging, which could potentially cross-contaminate ready-to-eat foods during and after purchase. Salmonella was detected on two (<1%) samples of external packaging (both from raw chicken), and Campylobacter was detected on 41 (1.1%) samples of external packaging. The external packaging of game fowl exhibited the highest Campylobacter contamination (3.6%), followed by raw chicken (3.0%), lamb (1.6%), turkey (0.8%), pork (0.2%), and beef (0.1%); Campylobacter jejuni and Campylobacter coli accounted for 59% (24 of 41) and 24% (10 of 41) of the contaminating Campylobacter species, respectively. C. coli isolates from the external packaging were more multiresistant to antimicrobial drugs, including quinolones such as ciprofloxacin, than was C. jejuni. Escherichia coli (an indicator of fecal contamination) was isolated from the external packaging on 4% of the raw meat samples at levels of 40 to 10(5) CFU per swab. The external packaging of raw meats is a vehicle for potential cross-contamination by Campylobacter, Salmonella, and E. coli in retail premises and consumers' homes. The external surface of heat-sealed packaging was less frequently contaminated with Campylobacter and E. coli compared with other types of packaging (e.g., overwrapping, bag, and tie tape) (P < 0.0001 to 0.01). In addition, external packaging of raw meats was contaminated less frequently with Campylobacter and E. coli when packaging was intact, packaging and display areas were visually clean, display temperatures were below 8 degrees C, and hazard analysis systems were in place.

Animals↗
PubMed1997

In vivo packaging of bacteriophage lambda monomeric chromosomes.

There is an apparent paradox between the reported requirements for lambda DNA packaging in vivo and in vitro. In vivo, DNA concatemers are required for packaging. On the other hand, in vitro, packaging extracts can encapsidate either linear or circular monomeric lambda DNA. Perhaps cellular nucleases restrict the in vivo ability of monomers to package by degrading a free double chain end present as an intermediate in the packaging reaction. Consistent with this hypothesis, enhanced packaging of monomers was found in an ExoV- host. No additional enhancement was noted in a host also mutant for sbcB and sbcC. We isolated a mutant phage for which in vivo packaging of monomeric lambda chromosomes is increased about 10(3)-fold. The responsible mutation (plm1 for packages lambda monomers) was mapped to cro, sequenced, and found to cause a change from Ala29 to Ser in the alpha3 helix of Cro's DNA binding domain. Density transfer experiments showed that packaging of both plm1 and wild-type lambda was aided by allowing some DNA synthesis. However, the packaged chromosomes had not themselves undergone a full round of replication and therefore were not part of a canonical concatemer made by replication. Other tests showed that packaged phage had not been part of concatemers made by recombination or by annealing at cos. Our results with wild-type lambda also favor models in which two cos sites are needed for packaging, but these sites need not be in cis. In lambda plm1, replication intermediates may serve as substrates for encapsidation.

Bacteriophage lambda↗
PubMed2002

The large subunit of bacteriophage lambda's terminase plays a role in DNA translocation and packaging termination.

The DNA packaging enzyme of bacteriophage lambda, terminase, is a heteromultimer composed of a small subunit, gpNu1, and a large subunit, gpA, products of the Nu1 and A genes, respectively. The role of terminase in the initial stages of packaging involving the site-specific binding and cutting of the DNA has been well characterized. While it is believed that terminase plays an active role in later post-cleavage stages of packaging, such as the translocation of DNA into the head shell, this has not been demonstrated. Accordingly, we undertook a generalized mutagenesis of lambda's A gene and found ten lethal mutations, nine of which cause post-cleavage packaging defects. All were located in the amino-terminal two-thirds of gpA, separate from the carboxy-terminal region where mutations affecting the protein's endonuclease activity have been found. The mutants fall into five groups according to their packaging phenotypes: (1) two mutants package part of the lambda chromosome, (2) one mutant packages the entire chromosome, but very slowly compared to wild-type, (3) two mutants do not package any DNA, (4) four mutants, though inviable, package the entire lambda chromosome, and (5) one mutant may be defective in both early and late stages of DNA packaging. These results indicate that gpA is actively involved in late stages of packaging, including DNA translocation, and that this enzyme contains separate functional domains for its early and late packaging activities.

Bacteriophage lambda↗
PubMed1995

Specific, nonproductive cleavage of packaged bacteriophage T7 DNA in vivo.

The morphogenesis of bacteriophage T7 includes assembly of a procapsid that subsequently both packages DNA and changes in structure. The DNA packaged by T7 is concatemeric and is cleaved to mature length during packaging. In the present study, packaged DNA obtained from T7-infected cells was analyzed after release from DNase-treated capsids. After fractionation by agarose gel electrophoresis, in-gel probing with oligonucleotides reveals that some of this DNA is shorter than mature T7 DNA; most of this short DNA has the T7 right end, but not the left end. Some of this short, packaged DNA is the product of left-to-right injection of DNA at the beginning of a T7 infection. However, subsequently produced short, packaged DNA has characteristics of a DNA that was produced during DNA packaging (incompletely packaged DNA or ipDNA). In contrast to results previously obtained in vitro, the profile of right-end-containing ipDNA is sometimes dominated by discrete bands. Some of the band-forming right-end-containing ipDNA appears with the kinetics of an abortive end product of packaging; cleavage in vivo appears to have arrested DNA packaging in this case. Other band-forming right-end-containing ipDNA appears with kinetics that have some characteristics expected of a precursor to the mature DNA; cleavage appears to have occurred after arrest of packaging in this case. The findings here of both left-to-right injection and right-to-left packaging is the most direct demonstration of polarity for these events in vivo.

Bacteriophage T7↗
PubMed1999

Nucleotides 1506-1625 of bovine papillomavirus type 1 genome can enhance DNA packaging by L1/L2 capsids.

We have previously described a DNA-packaging assay using bovine papillomavirus type 1 (BPV-1) virus-like particles (VLPs) and have identified a region of the BPV genome that assists in packaging. In this study, we identify a specific BPV sequence involved in DNA packaging by BPV-1 VLPs. In the initial screening of BPV-1 genomic sequences essential for DNA packaging, we observed that a plasmid with deletions between nucleotides (nt) 948 and 2113 failed to be packaged into BPV-1 VLPs. However, plasmids containing nt 948 to 2113 were efficiently packaged, suggesting that this 1.2-kb fragment contains a packaging enhancement sequence (PES). Further mapping of the BPV-1 genome showed that this packaging sequence lies between nt 1506 and 1625. Furthermore, this packaging sequence is also recognized by HPV6b VLPs, suggesting that a common packaging mechanism may be used by the two papillomavirus types. Given the phylogenetic difference between these two viral types, it is likely that other papillomavirus types may also use the same packaging mechanism. Identification of the PES has allowed a minimal viral genome sequence to be used in the packaging assay, improving the usefulness of the assay in studying the process of papillomavirus DNA encapsidation.

Animals↗
PubMed1992

DNA sequences necessary for packaging bacteriophage T3 DNA.

A recombinant plasmid, pUCE1-TR, carrying a target for processing of the concatemer joint (TR) and sequences to the left of the target (E1), is efficiently packaged into transducing particles during T3 phage infection. Using this plasmid packaging/transduction system, the minimal sequences necessary for packaging of T3 DNA were determined. The TR sequence contains the targets for initiation cleavage and termination cleavage of concatemer processing (pacCR and pacCL, respectively). A plasmid lacking pacCL was packaged as efficiently as pUCE1-TR but one deleted for pacCR was packaged at a very low efficiency, showing that pacCR is essential for production of transducers but that pacCL is dispensable. DNA from transducing particles carrying a recombinant plasmid lacking pacCL or pacCR had the same right or left end as T3 DNA, respectively, but its other end was not unique. In the absence of pacCL, packaging is initiated from the DNA end created by cleavage at the pacCR and terminated at any sequence after packaging a headful of DNA. In the absence of pacCR, packaging is initiated from the DNA end created by nonspecific, inefficient cleavage and terminated by cleavage at the pacCL after packaging a headful of DNA. A 23-bp segment flanking the site where the mature right end is formed was found to support efficient formation of transducing particles. A 53-bp sequence, including a consensus sequence for the promoter for T3 RNA polymerase, was a responsible element in the E1 sequence for packaging of plasmid DNA. Deletions of the 5'-upstream sequence of the promoter sequence from the left decreased the promoter and packaging activities in parallel, but with those of the 3'-downstream sequence from the right, the packaging activity was impaired before the promoter activity, indicating that transcription from the promoter is necessary but not sufficient for T3 DNA packaging.

Base Sequence↗
PubMed2004

cis-Acting packaging motifs of porcine adenovirus type 3.

The cis-acting packaging domain is required for selective encapsidation of adenovirus DNA into preformed empty capsids late in the viral life cycle. Earlier, it was demonstrated that the cis-acting packaging domain of porcine adenovirus type (PAdV)-3 is located between nucleotide position (nt) 212 and 531 at the left end genome which contains six AT/GC rich motifs. Removal of packaging domain from left end to the right end of the genome produced a viable mutant virus suggesting that the identified cis-acting packaging domain represents the DNA sequences required for selective packaging of PAdV-3 DNA, whose position and orientation appear to be flexible. Here, by constructing and analyzing a panel of virus mutants carrying deletions or linker scanning mutations in AT/GC rich sequences, we examined the significance of the continuous A/T or G/C sequences individually in the viral packaging process. In contrast to consensus bipartite structure (5'-TTTGN8CG-3') described for most of packaging motifs of human adenovirus type 5 (HAdV-5), the packaging motifs I, II, III, and IV of PAdV-3 displayed a tripartite structure in which the continuous A/T nucleotides were flanked by G/C-rich sequences. Mutations in both continuous A/T nucleotides and its flanking GC-rich sequences reduced the packaging efficiency of mutants to varying degrees. In addition, although the continuous A/T sequences were present in all of the packaging motifs, their significance in the packaging process appears to vary within each packaging motif.

Adenoviruses, Human↗
PubMed2002

Effects of some groundnut packaging methods and protection with Ocimum and syzygium powders on kernel infection by fungi.

Powders from the leaves of Ocimum gratissimum and cloves of Syzygium aromaticum were used as protectants at 3% (w/w) in combination with various packaging methods to store 3.5 kg groundnut kernel samples (9.3% moisture) artificially inoculated with Aspergillus parasiticus. Phostoxin-protected and unprotected samples were the controls. Packaging was accomplished with (i) Jute bags; JB (ii) Interlaced polypropylene bags; IPPB (iii) Polyethylene bags; PB (iv) PB inserted into IPPB and (v) PB inserted into JB. Selected treatments were repeated concurrently with naturally infected kernels (6.6% moisture). With 9.3% moisture kernels, there was a highly significant protectant, packaging method, and protectant X packaging method effect on protection of kernels from fungal infection at 2, 4, and 6 months. Packaging with JB and IPPB with or without plant powders gave 100% protection against fungi but insect infestation was prevented only when the Syzygium powder was used. When PB was used either singly or in combination with JB and IPPB, 100% protection from fungi was achieved up to 2 months with the Ocimum and up to 4 months with the Syzygium powder. The phostoxin treatment also gave 100% protection with JB and IPPB packaging but was ineffective with PB packaging. Kernels packaged with PB without the powders were extensively mouldy. Kernels with natural mycoflora (6.6% moisture) were free from fungi at 6 months regardless of the protectant and packaging used. In further tests, the Syzygium powder, at 3% and in combination with JB-packaging, effectively suppressed cross infection of healthy kernels (12% moisture) by fungi from diseased kernels when both kernel types occurred in the same lot. At 18.5% kernel moisture and with identical packaging, the Syzygium powder at 3%, was not as effective.

Aflatoxins↗
PubMed2002

Effectiveness of some recent antimicrobial packaging concepts.

A new type of active packaging is the combination of food-packaging materials with antimicrobial substances to control microbial surface contamination of foods. For both migrating and non-migrating antimicrobial materials, intensive contact between the food product and packaging material is required and therefore potential food applications include especially vacuum or skin-packaged products, e.g. vacuum-packaged meat, fish, poultry or cheese. Several antimicrobial compounds have been combined with different types of carriers (plastic and rubber articles, paper-based materials, textile fibrils and food-packaging materials). Until now, however, few antimicrobial concepts have found applications as a food-packaging material. Antimicrobial packaging materials cannot legally be used in the EU at the moment. The potential use would require amendments of several different legal texts involving areas such as food additives, food packaging, hygiene, etc. The main objective of this paper is to provide a state of the art about the different types of antimicrobial concepts, their experimental development and commercialization, and to present a case study summarizing the results of investigations on the feasibility of a low-density polyethylene (LDPE)-film containing triclosan to inhibit microbial growth on food surfaces and consequently prolong shelf-life or improve microbial food safety. In contrast with the strong antimicrobial effect in in-vitro simulated vacuum-packaged conditions against the psychrotrophic food pathogen L. monocytogenes, the 1000 mg kg(-1) containing triclosan film did not effectively reduce spoilage bacteria and growth of L. monocytogenes on refrigerated vacuum-packaged chicken breasts stored at 7 degrees C.

Animals↗
PubMed1999

Phthalates in paper and board packaging and their migration into Tenax and sugar.

Packaging samples for many kinds of foodstuffs were received from manufacturers together with basic information about the materials used in their production. Half of the 29 samples studied contained phthalates in amounts exceeding 5 mg/kg. Two types of paper bag intended for sugar and exceptionally high phthalate contents although they were flexo printed. The maximum contents of di-isobutylphthalate (DIBP) and dibutylphthalate (DBP) were 450 and 200 mg/kg, respectively. The phthalates found originated from adhesives used in the joints of the packaging. In other packagings manufactured at the same time, DIBP concentrations varied from 92 to 193 mg/kg. Phthalates were also determined in sugar before and after packaging. Migration of phthalates ranged from 57 to 74% of the original content in the packaging after 4 months storage. Packed sugar contained DIBP 2.2-2.6 mg/kg and DBP 0.5-1 mg/kg. The sugar packagings were also tested using Tenax as a food stimulant. The results indicated that 69-91% of the original content of the phthalates migrated into Tenex after 10 days at 40 degrees C. The major drawback with migration testing using Tenax is its high cost; it is not practical to fill the whole 1 kg packaging with Tenax, and smaller samples of packaging must be used instead. However, the distribution of substances in the packaging might be non-uniform. In the sugar packagings studied here, the difference between phthalate concentrations in two samples taken from the same packaging was nearly 100-fold.

Adhesives↗
PubMed1976

How effective is safety packaging?

Of 96 ingestions involving safety packaging, 82% involved misuse. The package in some way was unacceptable to the consumer--it was too difficult to open or too difficult to close. Nonacceptance by the elderly was not a significant factor. In only 18% of the safety packaged ingestions, did the child upen the package. The child was more likely to be able to open the screw-cap and the strip-pack. The pop-off and press-lift were not opened by any child but were types misused only by parents. The older child with a record of prior poisoning was most likely to open a safety package. These children would appear to represent a hard core of risk subjects refractory even to safety packaging. Safety packaging has had a dramatic effect on the morbidity and mortality of accidental poisoning. There are two remaining problems that require further study: 1. The analysis of technical factors impeding consumer acceptance and child proofing. The ideal package is so easily handled by the adult that misuse does not occur, but is too difficult for the child to open. 2. The personality characteristics of the safety-package-resistant child. Safety packaging, as implemented by the Comsumer Product Safety Commission, has had remarkable success. Education did not reduce accidental poisoning; safety packaging does. Pediatricians, pharmacists, and toxicologists must work with industry and the Consumer Product Safety Commission to complete the goal of elimination of accidental poisoning.

Aspirin↗
PubMed1999

Microbiological quality and production of botulinal toxin in film-packaged broccoli, carrots, and green beans.

The production of toxin by a 10-strain mixture of proteolytic Clostridium botulinum in fresh produce packaged in polyethylene films with different oxygen permeability was determined. Broccoli florets, shredded carrots, and green beans inoculated with approximately 10(2) C. botulinum spores per g were placed in bags (1.4 kg per bag) composed of four films with different oxygen transmission rates (OTRs). Broccoli was packaged in bags with OTRs of 3 (7,000 cm3/m2/24 h) and 4 (16,000 cm3/m2/24 h), and green beans were packaged in bags with OTRs of 2 (6,000 cm3/m2/24 h) and 4. Broccoli and green beans in bags were compressed and heat-sealed. Shredded carrots were packaged in bags with OTRs of 1 (3,000 cm3/m2/24 h) and 3 and vacuum-sealed. Produce was stored at 4, 13, and 21 degrees C for up to 27 (broccoli) or 28 (carrots and green bean) days and analyzed periodically. At each sampling time, gas composition within the bags, pH of the produce microbial population (total aerobic and anaerobic microorganisms, lactic acid bacteria, psychrotrophic bacteria, yeasts, and molds), and the presence or absence of botulinal toxin were determined. Packaging material affected the quality of vegetables, especially broccoli stored at 4 and 13 degrees C. For example, broccoli was scored as "good" after 22 days at 4 degrees C when it was packaged in film with higher gas permeability (OTR of 4), whereas broccoli appeared to be in "poor" condition when packaged in film with lower gas permeability (OTR of 3). With the exception of lactic acid bacteria, packaging material did not noticeably influence the growth of microorganisms. Lactic acid bacteria grew better in broccoli packaged in bags with an OTR of 3 than in those with an OTR of 4 at all temperatures. Botulinal toxin was detected in broccoli packaged in bags with an OTR of 3 and stored at 13 degrees C for 21 days and in those with an OTR of 4 and 3 and stored at 21 degrees C for 10 days. All toxic samples were visibly spoiled. Toxin was not detected in produce packaged under any other test conditions.

Botulinum Toxins↗
PubMed2000

BPV1 E2 protein enhances packaging of full-length plasmid DNA in BPV1 pseudovirions.

We studied determinants of efficient encapsidation of circular DNA, incorporating a PV early region DNA sequence (nt 584-1978) previously shown to enhance packaging of DNA within papillomavirus (PV)-like particles (VLPs). Insect coelomic cells (Sf-9) and cultured monkey kidney cells (Cos-1) were transfected with an 8-kb reporter plasmid incorporating the putative BPV packaging sequence and infected with BPV1 L1 and L2 recombinant baculovirus or vaccinia virus. Heavy (1.34 g/ml) and light (1.30 g/ml) VLPs were produced, and each packaged some of the input plasmid. In light VLPs, truncated plasmids, which nevertheless incorporated the PV-derived DNA packaging sequence, were more common than full-length plasmids. Packaging efficiency of the plasmid was estimated at 1 plasmid per 10(4) VLPs in both Cos-1 and Sf-9 cells. In each cell type, expression of the BPV1 early region protein E2 in trans doubled the quantity of heavy but not light VLPs and also increased the packaging efficiency of full-length circular plasmids by threefold in heavy VLPs. The resultant pseudovirions incorporated significant amounts of E2 protein. Pseudovirions, comprising plasmids packaged within heavy VLPs, mediated the delivery of packaged plasmid into Cos-1 cells, whereby "infectivity" was blocked by antisera to BPV1 L1, but not antisera to BPV1 E4. We conclude that (a) packaging of DNA within PV L1+L2 pseudovirions is enhanced by BPV1 E2 acting in trans, (b) E2 may be packaged with the pseudovirion, and (c) E2-mediated enhancement of packaging favors 8-kb plasmid incorporation over incorporation of shorter DNA sequences.

Animals↗
PubMed1985

Improved in vitro packaging of coliphage lambda DNA: a one-strain system free from endogenous phage.

In previous systems for in vitro packaging of lambda DNA, phages are produced from the packaging components as well as from added DNA. We have developed a new genetic strategy for in vitro packaging that bypasses this endogenous phage problem. Our system employs a single bacterial strain whose lambda prophage codes for all of the packaging proteins but is deleted for cos, the packaging origin. Crude extracts of the single lysogen: (i) are virtually free from endogenous phages, (ii) package added lambda DNA efficiently and (iii) are easy to prepare. Using the cos- in vitro packaging system we show that packaging of lambda linear monomers is a second-order reaction, but that packaging from concatemers prepared by annealing or ligation is first order. We conclude that in our cos- system, linear monomers are a poor substrate for in vitro packaging but that packaging from concatemers works well.

Bacteriophage lambda↗
PubMed1996

A randomised trial of two information packages distributed to new cancer patients before their initial appointment at a regional cancer centre.

The purpose of this study was to evaluate the extent to which a new patient information package (NPIP) or a mini version of the same package (mini-NPIP) reduces emotional distress and meets the informational needs of patients arriving at a tertiary cancer centre for the first time. A comprehensive package, NPIP, consisting of procedural information regarding cancer centre location, description of the health care team, treatment services, research, educational activities, accommodation and community services provided at the centre; and a condensed version of the same package, mini-NPIP, were developed. Consecutive patients with newly diagnosed breast, gynaecological, lung and prostate cancer, referred to the centre for the first time were prerandomised to receive NPIP, mini-NPIP or no information package. Patients randomised to NPIP or mini-NPIP were mailed the information package at least one week before their first appointment. On arrival at the centre, patients were administered the Brief Symptom Inventory (BSI) which measures psychological distress, and interviewed regarding preferences for information and acceptability of the information packages. Of 465 randomised patients, 161 were excluded post-randomisation and 304 completed the entire interview: 100 were randomised to the NPIP, 102 to the mini-NPIP and 102 to the control group. Emotional distress as measured by the BSI was similar for all groups (P = 0.98). Most patients preferred to receive the information (98%), receive it before the first appointment (84%) and by mail (79%). These preferences were more evident for those given the information packages. The majority of patients found the information packages easy to understand (88%) and useful (89%), and no differences were detected between packages. The cost of production and dissemination of NPIP was more than double the cost for mini-NPIP: $ 8.93 vs $ 3.98 (Canadian dollars) per patient. For patients presenting to a cancer centre for the first time, packages of procedural information do not appear to reduce psychological distress, but are preferred by patients. Given the cost of producing NPIP, mini-NPIP is the preferred approach.

Feasibility Studies↗
PubMed1986

In vitro packaging of foreign DNA into heads of bacteriophage T1.

The isolation of a collection of 44 morphologically T1-like phages is described. It is shown that these phages share some similarity with T1 in terms of cross-inactivation with anti-T1 serum, particle proteins and DNA packaging in vitro by the headful process. Virion DNA extracted from these phages was treated with T1 in vitro packaging extracts and the reaction mixtures were tested for the formation of infectious phage particles. The packaging efficiencies observed varied from about 1 to 100% of that of virion T1 DNA. Phage lambda virion DNA was packaged with an efficiency of between 0.01 and 2% (5 X 10(1) to 3 X 10(3) p.f.u./micrograms DNA), the shorter deleted derivative lambda L47 being packaged more efficiently than normal length lambda C1857 DNA. Virion DNA from phages T3 and T7 was also packaged at an efficiency similar to that for lambda. The in vitro packaging of T1 DNA requires the presence of the pac sequence which initiates headful packaging from a concatemeric precursor. The high efficiency of packaging DNA from some of the T1-like phages may indicate the presence of similar packaging sequences. However, in the case of lambda L47, which is known not to contain such a sequence, the in vitro DNA packaging reaction must occur by a secondary pathway unrelated to the headful mechanism.

Bacteriophage lambda↗
PubMed1995

Virus DNA packaging: the strategy used by phage lambda.

Phage lambda, like a number of other large DNA bacteriophages and the herpesviruses, produces concatemeric DNA during DNA replication. The concatemeric DNA is processed to produce unit-length, virion DNA by cutting at specific sites along the concatemer. DNA cutting is co-ordinated with DNA packaging, the process of translocation of the cut DNA into the preformed capsid precursor, the prohead. A key player in the lambda DNA packaging process is the phage-encoded enzyme terminase, which is involved in (i) recognition of the concatemeric lambda DNA; (ii) initiation of packaging, which includes the introduction of staggered nicks at cosN to generate the cohesive ends of virion DNA and the binding of the prohead; (iii) DNA packaging, possibly including the ATP-driven DNA translocation; and (iv) following translocation, the cutting of the terminal cosN to complete DNA packaging. To one side of cosN is the site cosB, which plays a role in the initiation of packaging; along with ATP, cosB stimulates the efficiency and adds fidelity to the endonuclease activity of terminase in cutting cosN. cosB is essential for the formation of a post-cleavage complex with terminase, complex I, that binds the prohead, forming a ternary assembly, complex II. Terminase interacts with cosN through its large subunit, gpA, and the small terminase subunit, gpNu1, interacts with cosB. Packaging follows complex II formation. cosN is flanked on the other side by the site cosQ, which is needed for termination, but not initiation, of DNA packaging. cosQ is required for cutting of the second cosN, i.e. the cosN at which termination occurs. DNA packaging in lambda has aspects that differ from other lambda DNA transactions. Unlike the site-specific recombination system of lambda, for DNA packaging the initial site-specific protein assemblage gives way to a mobile, translocating complex, and unlike the DNA replication system of lambda, the same protein machinery is used for both initiation and translocation during lambda DNA packaging.

Amino Acid Sequence↗