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Biomedical subjects

R F Weaver

Publications and source records attributed to R F Weaver.

At least 37 records · Page 2Linked to original sources
PubMed1988

Construction of a recombinant expression plasmid encoding a staphylococcal protein A-ricin A fusion protein.

A recombinant plasmid has been constructed containing the coding regions for a functional fragment of staphylococcal protein A and the entire ricin A chain in tandem in the same reading frame. The recombinant gene has been expressed in Escherichia coli cells to produce a protein with both staphylococcal protein A activity and ricin A chain activity. Such a fusion protein could be used for producing immunotoxins.

Cell Line↗
PubMed1986

Nucleotide sequence of a portion of the Autographa californica nuclear polyhedrosis virus genome containing the EcoRI site-rich region (hr5) and an open reading frame just 5' of the p10 gene.

The nucleotide sequence of a 1587 bp region lying within the HindIII-Q fragment of Autographa californica multiple nucleocapsid nuclear polyhedrosis virus (AcMNPV) DNA has been determined. It begins in the EcoRI-S-EcoRI-X region, continues to the HindIII-P/Q boundary and contains an open reading frame that codes for a polypeptide of 240 amino acids (p26). This open reading frame is also included in the 1100 and 1500 base transcripts previously mapped to this region. The sequence reveals that the 5' ends of the 1100 and 1500 base transcripts are located 20 bp downstream from the end of a putative TATA box (TAATTAAAT) and 19 bp upstream from the translation start codon (ATG) of the p26 open reading frame. The translation termination codon (TAA) falls in the immediate 5' flanking region of the major late p10 gene of AcMNPV, 3 bp downstream from the putative TATA box. The probable polyadenylation site for the 1100 base transcript lies 23 bp downstream from the cap site for the 750 and 2500 base transcripts encoding the p10 protein. The 5' flanking region of the p26 open reading frame contains the EcoRI site-rich region, hr5, whose sequence is included here. The EcoRI site-rich region, hr5, consists of six imperfect tandem repeats of a sequence that includes the EcoRI recognition site. These direct repeats also include many inverted repeats.

Amino Acid Sequence↗
PubMed1986

Physical mapping of temporally regulated, overlapping transcripts in the region of the 10K protein gene in Autographa californica nuclear polyhedrosis virus.

We investigated transcriptional activity in the region of a gene for a major late protein (10 kilodaltons) of Autographa californica nuclear polyhedrosis virus. This 10K protein gene spans an HindIII cleavage site, with the 5' end of the gene located in the HindIII-Q fragment and the 3' end in the HindIII-P fragment. Northern blot analysis showed that there were at least four transcripts mapping in this region, two that are present maximally at 12 h (1,500 and 1,100 bases in length) and two that are present at 24 h (750 and 2,500 bases in length). Northern blot analysis also suggested that these transcripts overlap. S1 mapping identified the precise positions of the transcripts and confirmed the overlap. The 1,500- and 1,100-base transcripts share a common 5' end, about 1,056 bases upstream from the HindIII-P-Q boundary; the 750- and 2,500-base transcripts share a common 5' end, about 303 bases upstream from the HindIII-P-Q boundary. The 1,100-base transcript terminates in the Q fragment, about 234 bases from the HindIII-P-Q boundary. The other three transcripts all end in the P fragment. Both the 1,500- and the 750-base transcripts terminate approximately 240 bases from the HindIII-P-Q boundary. The 2,500-base transcript exhibits 3'-end heterogeneity, ending around 2,046 bases from the HindIII-P-Q boundary. Therefore, three different transcripts (1,500, 750, and 2,500 bases in length) contain the complete 10K protein coding region. A fourth transcript (1,100 bases in length) overlaps the 750-base 10K protein gene transcript by 70 bases.

DNA Restriction Enzymes↗
PubMed1985

Genomic cloning and characterization of a ricin gene from Ricinus communis.

A genomic clone that specifies a single polypeptide precursor for ricin, a toxic lectin of Ricinus communis (castor bean), was isolated, sequenced and Sl mapped. The gene encodes a 64 kDa precursor which contains, in the following order: a 24 or 35 amino acid signal peptide, the A chain, a 12 amino acid linker peptide, and the B chain. The 5'-end of the ricin mRNA maps approximately 35 bases upstream from the first methionine codon. Two putative TATA boxes and a possible CAAT box lie in the 5'-flanking region. Two possible polyadenylation signals were found in the 3' flanking region. No introns were found, which is typical of other lectin genes that have been sequenced. Southern blot analysis suggests that the castor bean genome contains approximately six ricin-like genes.

Amino Acid Sequence↗
PubMed1983

Viral Transcription During Autographa californica Nuclear Polyhedrosis Virus Infection: a Novel RNA Polymerase Induced in Infected Spodoptera frugiperda Cells.

Autographa californica nuclear polyhedrosis virus-specific RNA synthesis in isolated nuclei of Spodoptera frugiperda cells in culture was monitored at different times postinfection. Up to 8 h postinfection viral RNA synthesis remained sensitive to 5 mug of alpha-amanitin per ml. During the course of infection this sensitivity decreased, and at 24 h postinfection RNA synthesis was completely resistant to alpha-amanitin. DEAE-Sephadex profiles of RNA polymerase isolated at 24 h postinfection showed a new, chromatographically distinct, alpha-amanitin-resistant form whose kinetics and response to divalent cations differed from those of the host RNA polymerases. The possibility that this enzyme may be responsible for viral late transcription is discussed.

Journal Article↗
PubMed1982

Capping of Viral RNA in Cultured Spodoptera frugiperda Cells Infected with Autographa californica Nuclear Polyhedrosis Virus.

Viral RNA from fall armyworm (Spodoptera frugiperda) cells infected with Autographa californica nuclear polyhedrosis virus contains cap structures. Most of the cap labeled in vivo with [(3)H]methionine or (32)P(i) cochromatographed on DEAE-cellulose with the -5 charge marker; a minor component appeared at -4 net charge. The former is probably a cap 1 structure (m(7)GpppX(m) (p)Yp), and the latter is probably a cap 0 (m(7)GpppXp). On the basis of relative labeling of the two caps with [(3)H]adenosine and [(3)H]guanosine, we concluded that each cap contained at least one adenosine residue in addition to guanosine and, therefore, that cap 0 contained m(7)GpppAp. Cleavage of [(3)H]methionine-labeled viral RNA with tobacco acid pyrophosphatase released a labeled component that cochromatographed on polyethyleneimine-cellulose with m(7)Gp, confirming the m(7)GpppX linkage in the cap. These results were also seen with host polyadenylated RNA. The caps appeared in nearly equal abundance in viral polyadenylated and non-polyadenylated RNAs. The ratio of (32)P(i) incorporated into the cap to that incorporated into mononucleotides suggested average lengths for the polyadenylated and non-polyadenylated RNAs of 1,800 and 1,200 nucleotides, respectively.

Journal Article↗
PubMed1981

alpha-Amanitin-Resistant Viral RNA Synthesis in Nuclei Isolated from Nuclear Polyhedrosis Virus-Infected Heliothis zea Larvae and Spodoptera frugiperda Cells.

[(3)H]RNA was synthesized in nuclei isolated at various times postinfection from the fat bodies of Heliothis zea larvae infected with H. zea nuclear polyhedrosis virus and from cultured Spodoptera frugiperda cells infected with Autographa californica nuclear polyhedrosis virus. To detect virus-specific RNA synthesis, the [(3)H]RNA was hybridized to denatured viral DNA immobilized on nitrocellulose filters. Nuclear polyhedrosis virus-specific RNA synthesis in the infected nuclei isolated from H. zea larval fat bodies and S. frugiperda cells was only inhibited 20 to 25% by concentrations of alpha-amanitin sufficient to inhibit the host RNA polymerase II. In addition, a productive nuclear polyhedrosis virus infection was obtained in S. frugiperda cells grown in the presence of an alpha-amanitin concentration that inhibited 90% of the cellular RNA polymerase II activity. The cellular RNA polymerase II enzyme remained sensitive to alpha-amanitin during infection, and there was no evidence that a virus-coded, alpha-amanitin-resistant enzyme was synthesized after the onset of infection. The data suggest that the bulk of nuclear polyhedrosis virus-specific RNA synthesis in isolated nuclei is transcribed by an enzyme other than the host RNA polymerase II.

Journal Article↗
PubMed1980

Vitellogenin: its structure, synthesis and processing in the cockroach Periplaneta americana.

The vitellogenin in the oocyte of the American cockroach contains three different polypeptides with approximate molecular weights of 123 000, 118 000 and 57 000. These are present in a molar ratio of 2 : 2 : 2; all three contain carbohydrate. The same subunit structure is observed in vitellogenin isolated from hemolymph and in that secreted by fat body in organ culture. The only protein found within fat body by precipitation with female-specific antiserum is a large polypeptide, with a molecular weight of approx. 250 000. No mature vitellogenin subunits are found in fat body, even after pulsing with labeled amino acids and chasing with unlabeled substrates for up to 4 h. These data suggest that vitellogenin is synthesized in the fat body as a large precursor, which is processed to smaller polypeptides upon secretion into the hemolymph.

Animals↗
PubMed1979

Mapping of RNA by a modification of the Berk-Sharp procedure: the 5' termini of 15 S beta-globin mRNA precursor and mature 10 s beta-globin mRNA have identical map coordinates.

We have used a modification of the Berk-Sharp technique to determine that the 5' termini of the mouse 15 S beta-globin precursor and the mature mRNA have identical map coordinates. The modification involves the use of 5' (or 3') terminally labeled probes; it allows the detection of the precursor in the presence of excess mature mRNA.

Animals↗
PubMed1977

CNDO molecular orbital calculations on porphyrins--I. Ground and excited states of porphyrin, divinylporphyrin and tetraphenylporphyrin.

Semi-empirical CNDO/2 MO calculations are reported for the ground states of porphyrin, 2,4-divinylporphyrin (DVP), and alpha, beta, gamma, delta-tetraphenylporphyrin (TPP). Results for TPP refer to the conformation with all phenyl groups perpendicular to the porphyrin ring, calculated to be 108 kJ mol-1 more stable than the coplanar conformation. The substituents withdraw electron density where they are attached to the porphyrin ring, increasing selected orbital energies. The vinyl groups also modify the electron population at nitrogen. CNDO/S calculations with extensive configuration interaction are reported for excited states. The lowest singlet states are closely similar in energy and composition for all three molecules, except for an extra state and more complex compositions in DVP above 3 eV. The lowest triplet states of porphyrin and DVP are very similar, while those of TPP are comparable in energy or composition but not both. Experimental data on the excited states are broadly consistent with the calculations, although comparisons for the excited triplets are tentative.

Molecular Conformation↗
PubMed1977

CNDO molecular orbital calculations on porphyrins--II. Ground states of dilithium and disodium porphyrin.

CNDO/2 calculations are reported for dilithium and disodium porphyrin. The total energy is calculated as a function of the metal-ring distance for symmetrical (D4h) structures. For dilithium porphyrin, the equilibrium metal-ring distance is 0.87 A and the metal-metal vibrational frequency is 123 cm-1. For disodium porphyrin, the distance is 1.64 A and the frequency is 77 cm -1. Little mixing of metal and porphyrin orbitals takes place; the two lowest unoccupied and the two highest occupied MOs hardly differ from those in porphyrin, but lower MOs are considerably rearranged.

Lithium↗
PubMed1977

Structural studies on the polyhedral inclusion bodies, virions, and DNA of the nuclear polyhedrosis virus of the cotton bollworm Heliothis zea.

The polyhedral inclusion body of the cotton bollworm nuclear polyhedrosis virus contains virions occluded in an orthogonal crystalline matrix. The virions appear as rods or, more frequently, as oval structures that form upon bending of the nucleocapsid within the viral membrane. The nucleocapsid consists at least of DNA surrounded by a capsid composed of subunits, possibly helically arranged. The viral DNA is circular and supercoiled. It is heterogenous in size with contour lengths ranging from 15 to 45 mum.

Animals↗
PubMed1976

Photoreceptor pigment that induces differentiation in the slime mold Physarum polycephalum.

An extract of small molecules (molecular weight less than 500) of the slime mold Physarum polycephalum undergoes a shift in ultraviolet-visible absorption spectrum upon illumination. This illumination also confers on the extract the ability to induce sporulation when injected into a starved, unilluminated slime mold. The spectral shift and appearance of the sporulation-inducing activity both occur regardless of whether the illumination is carried out on an intact slime mold or on the plasmodium-free extract itself. Thin-layer chromatography resolves the slime mold extract into four major visible fractions. One of these has high sporulation-inducing activity after illumination in vitro.

Cell Differentiation↗