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Biomedical subjects

A Richardson

Publications and source records attributed to A Richardson.

At least 55 records · Page 3Linked to original sources

Self-handicapping status, claimed self-handicaps and reduced practice effort following success and failure feedback.

BACKGROUND: Self-handicapping involves the strategic establishment of an impediment or obstacle to success prior to a performance situation which thereby provides a convenient excuse for poor performance. AIMS: The study sought to establish that relative to low trait self-handicappers, high trait self-handicappers exposed to failure in an intellectually evaluative situation will (a) pre-emptively claim more handicaps, and (b) behaviourally self-handicap through reduced practice effort, and (c) report greater anxiety and negative affect relative to low trait self-handicappers. SAMPLE: Participants were 72 undergraduate students, divided equally between high and low self-handicapping groups. METHOD: This study utilised a 2 (self-handicapping status: high, low) x 3 (performance feedback: fail, low task importance; fail, high task importance; success) between-subjects factorial design to investigate claimed and behavioural self-handicapping through reduced practice effort. This was done by manipulating performance outcome and perceived task importance. RESULTS: Relative to low trait self-handicappers, high trait high self-handicappers claimed more handicaps and engaged in greater behavioural self-handicapping following failure when working on tasks that were described as potentially diagnostic of low ability. While low self-handicappers internalised their success more than their failure in the high task importance condition, high self-handicappers were undifferentiated in their attributions across performance conditions. Greater anxiety and greater negative affect were also characteristic of high self-handicappers. CONCLUSIONS: The study highlights the self-protective benefit of self-handicapping in sparing the individual from conclusions of low ability, and the failure of high self-handicappers to fully internalise their success. These elements and the role of uncertain estimates of ability are discussed in considering implications for intervention.

Achievement↗

Issues in methodological research: perspectives from researchers and commissioners.

OBJECTIVES: (1) Methodological research has few well-defined tools and processes analogous to those available for reviews and data collection in substantive health technology assessment. (2) This project was set up to obtain researchers' and others' views on the innovative projects on research methodology under the NHS Health Technology Assessment Programme and the usefulness of the research. (3) The study was intended to span both epistemological and management issues. (4) The following issues were explored: (a) the degree to which researchers would feel constrained by the "Cochrane" approach to systematic reviews when undertaking reviews of a methodological nature; (b) whether methodological projects may require exceptional design and management arrangements, in view of their novelty, subjectivity and complexity; (c) whether researchers would seek out other methods, in addition to undertaking reviews of argument, as a means of extending their understanding of methodological issues (there may be three categories of research methods in methodology: reviews of methodological argument, studies that use the literature as a source of data, and research that collects new primary data); (d) whether the Methodology Programme overall can be considered a "success". METHODS: (1) Telephone interviews were carried out on researchers (one senior and one junior per project), resulting in 35 interviews from 19 of the 20 target projects. (2) A qualitative postal survey was sent to 12 people who had played a key role in the development of the Methodology Programme; replies were received from six of them. (3) Analysis was undertaken of the hit rates for 29 projects on the NCCHTA website by the end of February and the end of May 1999, comparing those concerned with methodology (n = 10) and those concerned with other issues (n = 19). RESULTS: UNDERTAKING METHODOLOGICAL RESEARCH: VIEWS OF RESEARCHERS: This section summarises the views of 35 researchers who were interviewed by telephone. RESULTS: UNDERTAKING METHODOLOGICAL RESEARCH: VIEWS OF RESEARCHERS: (THE NATURE OF METHODOLOGICAL REVIEWS): (1) There was a reluctance among researchers to use the term "systematic review" in the methodological context. (2) Practical problems in undertaking methodological reviews were found at every stage of the research process. (a) In the initial search stage, preplanned strategies were difficult to maintain, owing to the need to respond to the problems of too few or too many references. (b) At the analysis stage, most studies were not formally weighted, but there was implicit weighting in researchers' views of their merits or relevance. (c) It was often only at the synthesis stage that researchers could see clearly what their study was able to do; iteration was frequently necessary at this point. (d) It was difficult to form simple conclusions and recommendations beyond summaries of what was known in the field. (e) Dissemination activities were most often directed to other health service researchers, with some attention to NHS policy makers and research commissioners. RESULTS: UNDERTAKING METHODOLOGICAL RESEARCH: VIEWS OF RESEARCHERS (THE NEED FOR FLEXIBILITY): (1) Few researchers had amended their topic or methods once their research was under way, although some had made minor changes to their original plan, generally to refine the topic to fit the time or data available. (2) Changing a topic was seen as inappropriate unless checked with funders, but changes in research methods were viewed as reasonable because questions might be refined in the light of information gained or early thinking. RESULTS: UNDERTAKING METHODOLOGICAL RESEARCH: VIEWS OF RESEARCHERS (THE QUESTION OF BIAS): (1) Few researchers considered that this kind of research could be undertaken or presented in a wholly unbiased way because of the need to assess the research studied. (2) Objectivity was nonetheless seen as something that researchers should strive towards. Efforts to do so included presenting data clearly, separating findings from discussion, covering all points of view, setting out their own assumptions and values, and testing their ideas on others known to have differing views. (3) The formal peer-review process was not seen to have made a difference here, primarily because of the stage at which referees become involved. RESULTS: UNDERTAKING METHODOLOGICAL RESEARCH: VIEWS OF RESEARCHERS (PROJECT MANAGEMENT--TIMING AND TIME MANAGEMENT): (1) A majority of projects were completed within 3 months of their due date. Those studies completed roughly on time were considered to have efficient junior researchers and good project management, including clear deadlines for different stages of the research. (2) Some studies had severe problems of time management. Too much time tended to be spent on collecting and reading the literature and the writing stage was not always well planned. Referees' comments were also slow in coming. (ABSTRACT TRUNCATED)

Attitude↗

The utility of ultrasonographically guided large-core needle biopsy: results from 500 consecutive breast biopsies.

Five hundred ultrasonographically guided large-core needle breast biopsies of solid masses were performed in 446 women. Histopathologic results were correlated with imaging findings. Ultrasonographically guided large-core needle biopsy resulted in diagnosis of malignancy (n = 124) or severe atypical ductal hyperplasia (n = 4) in 128 lesions (26%). In the remaining 372 lesions (74%), ultrasonographically guided large-core needle biopsy yielded benign pathologic results. Follow-up of more than 1 year (n = 225), results of surgical excision (n = 50), or both were obtainable in 275 (74%) of the benign lesions. No malignancies were discovered at surgical excision or during follow-up of this group of benign lesions. There were no complications related to large-core needle biopsy that required additional treatment. Ultrasonographically guided large-core needle biopsy is a safe and accurate method for evaluating breast lesions that require tissue sampling.

Adolescent↗

Pseudo-T-even bacteriophage RB49 encodes CocO, a cochaperonin for GroEL, which can substitute for Escherichia coli's GroES and bacteriophage T4's Gp31.

Bacteriophage T4-encoded Gp31 is a functional ortholog of the Escherichia coli GroES cochaperonin protein. Both of these proteins form transient, productive complexes with the GroEL chaperonin, required for protein folding and other related functions in the cell. However, Gp31 is specifically required, in conjunction with GroEL, for the correct folding of Gp23, the major capsid protein of T4. To better understand the interaction between GroEL and its cochaperonin cognates, we determined whether the so-called "pseudo-T-even bacteriophages" are dependent on host GroEL function and whether they also encode their own cochaperonin. Here, we report the isolation of an allele-specific mutation of bacteriophage RB49, called epsilon22, which permits growth on the E. coli groEL44 mutant but not on the isogenic wild type host. RB49 epsilon22 was used in marker rescue experiments to identify the corresponding wild type gene, which we have named cocO (cochaperonin cognate). CocO has extremely limited identity to GroES but is 34% identical and 55% similar at the protein sequence level to T4 Gp31, sharing all of the structural features of Gp31 that distinguish it from GroES. CocO can substitute for Gp31 in T4 growth and also suppresses the temperature-sensitive phenotype of the E. coli groES42 mutant. CocO's predicted mobile loop is one residue longer than that of Gp31, with the epsilon22 mutation resulting in a Q36R substitution in this extra residue. Both the CocO wild type and epsilon22 proteins have been purified and shown in vitro to assist GroEL in the refolding of denatured citrate synthase.

Amino Acid Sequence↗

The importance of a mobile loop in regulating chaperonin/ co-chaperonin interaction: humans versus Escherichia coli.

Chaperonins are universally conserved proteins that nonspecifically facilitate the folding of a wide spectrum of proteins. While bacterial GroEL is functionally promiscuous with various co-chaperonin partners, its human homologue, Hsp60 functions specifically with its co-chaperonin partner, Hsp10, and not with other co-chaperonins, such as the bacterial GroES or bacteriophage T4-encoded Gp31. Co-chaperonin interaction with chaperonin is mediated by the co-chaperonin mobile loop that folds into a beta-hairpin conformation upon binding to the chaperonin. A delicate balance of flexibility and conformational preferences of the mobile loop determines co-chaperonin affinity for chaperonin. Here, we show that the ability of Hsp10, but not GroES, to interact specifically with Hsp60 lies within the mobile loop sequence. Using mutational analysis, we show that three substitutions in the GroES mobile loop are necessary and sufficient to acquire Hsp10-like specificity. Two of these substitutions are predicted to preorganize the beta-hairpin turn and one to increase the hydrophobicity of the GroEL-binding site. Together, they result in a GroES that binds chaperonins with higher affinity. It seems likely that the single ring mitochondrial Hsp60 exhibits intrinsically lower affinity for the co-chaperonin that can be compensated for by a higher affinity mobile loop.

Amino Acid Sequence↗

cDNA expression arrays reveal incomplete reversal of age-related changes in gene expression by calorie restriction.

Calorie restriction (CR) extends life span and retards many age-related cellular and molecular changes in laboratory rodents. However, neither the breadth of its effects, its underlying mechanisms, nor the limits of its action is fully understood. Expression levels of 588 genes in livers from 3- and 24-month-old ad libitum-fed (AL), and 24-month-old CR (60% of AL intake) male C57BL/6J mice (four per group) were measured. Six genes met the statistical criteria for differential expression in old AL compared to young AL mice. Only one of these age-related changes was attenuated by CR. Four additional gene products, that did not change with age in AL mice, were differentially expressed in old CR compared to old AL mice. Northern and RT-PCR analyses confirmed differential expression of four of the six candidate genes identified by the array results. Many of the identified genes have not previously been reported to be affected by CR or aging. Some of the age-related changes in gene expression are consistent with an increased vulnerability of the aged liver to carcinogenic or other insults, with only partial protection against insult by CR. Incomplete reversal by CR of age-related changes in gene expression provides a potentially important path for probing the limits of CR action. These results also show the importance of independent confirmation in expression array profiling of age-related changes in gene expression.

Aging↗

Age-related alterations in the activation of heat shock transcription factor 1 in rat hepatocytes.

The induction of hsp70 transcription by heat shock is significantly reduced in hepatocytes isolated from old rats compared to hepatocytes isolated from young/adult rats, and the decline in hsp70 transcription is correlated with a decrease in the induction of heat shock transcription factor 1 (HSF1) binding to the heat shock element. However, the decreased HSF1 binding activity to DNA is not due to reduced levels of HSF1 that are available for activation by heat shock. In fact, the levels of HSF1 are two- to threefold higher in hepatocytes from old rats, and the age-related increase in the levels of HSF1 protein in hepatocytes appears to arise from a decrease in the degradation of the HSF1 because HSF1 mRNA levels do not change and the synthesis of HSF1 decreases approximately 50% with age. No evidence was found for an impairment in HSF1 oligomerization in hepatocytes from old rats, e.g., the level of HSF1 trimers, the nuclear translocation of HSF1, and the phosphorylation of HSF1 after heat shock are similar in hepatocytes isolated from young/adult and old rats. However, the thermostability of the DNA binding activity of HSF1 was significantly reduced with age in a cell-free system as well as in isolated hepatocytes.

Aging↗

Normal immune function in young and old DNA polymerase-beta deficient mice.

The effect of the DNA polymerase-beta (beta-pol) deficiency on mitogenic response and cytokine production was studied in spleen lymphocytes from 4-5- and 20-22-month-old beta-pol(-/+) mice and their age-matched wild-type littermates. The proliferative response of lymphocytes to Concanavalin A (Con A) and lipopolysaccharide (LPS) was measured by [3H]thymidine incorporation, and the induction of cytokine production (interleukin (IL)-2, IL-4, and interferon necrosis factor (IFN)-gamma) was assessed by enzyme-linked immunosorbent assay. There was no significant difference in Con A- or LPS-induced proliferation or cytokine production in young beta-pol(-/+) mice compared with young wild-type littermates or in old beta-pol(-/+) mice compared with old wild-type littermates. However, mitogen-induced proliferation and cytokine production changed significantly with age. The proliferative response to Con A and to LPS, and the IL-2 production was significantly lower, and IL-4 and IFN-gamma levels were significantly higher in lymphocytes from old beta-pol(-/+) mice and old wild-type mice than in lymphocytes from young beta-pol(-/+) mice and young wild-type littermates. In addition, flow cytometric analysis showed no significant differences between young beta-pol(-/+) mice and young wild-type littermates or between old beta-pol(-/+) mice and old wild-type littermates in the proportion of B- and T-cell populations, and T-cell subsets. However, the number of lymphocytes expressing CD4+ phenotype slightly decreased and the proportion of lymphocytes expressing CD44/Pgp-1 (memory) phenotype increased with age. Thus, we found no evidence for alteration in immune function in DNA polymerase-beta deficient mice, although they exhibit a decline in immunologic function with age.

Aging↗

Using MT(-/-) mice to study metallothionein and oxidative stress.

Mice with null mutations for metallothionein genes MT-1 and MT-2 were used to study the role that metallothionein plays in protecting cellular targets in vivo from oxidative stress. Wild-type (MT(+/+)) and MT-null (MT(-/-)) mice were treated with either saline or zinc and exposed to two types of oxidative stress: gamma-irradiation or 2-nitropropane. There was no alteration in the antioxidant defense system (superoxide dismutase, catalase, or glutathione peroxidase and glutathione levels) to compensate for the lack of the metallothionein in the MT(-/-) mice. The amount of oxidative damage to liver DNA, lipids, and proteins were similar for the MT(-/-) and MT(+/+) mice even though the levels of metallothionein in the livers of the saline- or zinc-pretreated MT(+/+) mice were 5- to 100-fold greater than found in the MT(-/-) mice. To determine if metallothionein can protect mice from the lethal effects of ionizing radiation, the mean survivals of MT(-/-) and MT(+/+) mice exposed to whole body gamma-irradiation were measured and found to be similar. However, the mean survival increased significantly after zinc pretreatment for both the MT(-/-) and MT(+/+) mice. These results demonstrate that tissue levels of metallothionein do not protect mice in vivo against oxidative stress.

8-Hydroxy-2'-Deoxyguanosine↗

Cancer-related fatigue: inevitable, unimportant and untreatable? Results of a multi-centre patient survey. Cancer Fatigue Forum.

OBJECTIVES: To investigate cancer patients' experience of fatigue and their perceptions about the causes, management and impact of this symptom. DESIGN: Cross-sectional, questionnaire-based survey. SETTINGS: Three regional cancer centres; Glasgow, Birmingham and Southampton. PARTICIPANTS: One thousand three hundred seven outpatients with cancer attending the three units over a 30-day period. MAIN OUTCOME MEASURES: Investigator designed questionnaire and the fatigue sub-scale of the Functional Assessment of Cancer Therapy Fatigue (FACT-F) questionnaire. RESULTS: The response rate was 576 of 1307 (44%). Fatigue was reported to affect 58% of patients 'somewhat or very much'. The comparable figures for pain and nausea/vomiting were 22% and 18%, respectively. Fatigue had never been reported to the hospital doctor by 52% (281 of 538) of patients with this symptom. Only 75 patients (14%) had received treatment or advice about the management of their fatigue. Fatigue was reported to be not well-managed by 33% (180 of 538) of patients with this symptom. The comparable figures for pain and nausea/vomiting were 9% (46 of 538) and 7% (37 of 538), respectively. The median FACT-F score was 18 (range 0-52). On multivariate analysis 54% of the variation in FACT-F scores could be explained by the combination of quality of life, depression, dyspnoea, weight loss/anorexia and use of analgesics in the previous month. CONCLUSIONS: Fatigue has been identified as an important problem by patients with cancer. It affects more patients for more of the time than any other symptom and is regarded by patients as being more important than either pain or nausea/vomiting. Research into the aetiology and management of this symptom should be regarded as a priority.

Adolescent↗

Interceptive orthodontics in the real world of community dentistry.

OBJECTIVE: To test the applicability and effectiveness of interceptive orthodontics in a community field trial. DESIGN: Prospective screening for suitable malocclusions, implementation of treatment and analysis of outcomes 12 months later. SETTING: Community dentistry in urban and rural areas of Northern Ireland, 1996-98. SUBJECTS AND METHODS: The initial sample consisted of 2002 children (1014 boys, 988 girls) who were screened in routine community dental inspections. One thousand and sixty (523 aged 9 years, 537 aged 11 years) were domiciled in the urban area of greater Belfast and 942 (479 aged 9 years, 463 aged 11 years) in the rural area of Enniskillen and Omagh, Co. Tyrone. INTERVENTIONS: Interceptive orthodontic treatment. OUTCOME MEASURES: Dental health component of the Index of Orthodontic Treatment Need (IOTN) and specially devised local indices of treatment outcomes. RESULTS: With the use of an interception gauge, orthodontic screening was included in the community dental inspections without difficulty. Thirty-three per cent of children were in need of interceptive treatment. Only 20% of those in need both attended for recall and underwent treatment. Compliance was better in the rural area but the need, with particular reference to extraction of carious first molars, was greater in the urban area. The numbers of children in IOTN grades 4 and 5 fell from 69% at the beginning of the study to 42% at the end. The outcome judged by local indices was 94% in the range of complete success to minimal improvement with only 2% showing deterioration. CONCLUSIONS: One in three children screened in community dental inspections at age 9 and 11 years would benefit from interceptive orthodontics. Parents and children seem reluctant to accept offers of interceptive orthodontics and to having the treatment carried out. Among those complying fully, the interceptive measures are very successful. Not only does community interceptive orthodontics improve the condition being treated but also reduces the need for further treatment.

Chi-Square Distribution↗

Oxidase activity in lignifying xylem of a taxonomically diverse range of trees: identification of a conifer laccase.

In a diverse taxonomic range of tree species, including representative species of ancient families of angiosperms (Magnolia x soulangiana Soul.-Bod.) and gymnosperms (Ginkgo biloba L.), oxidase activity was associated with cell walls of developing xylem and was enriched in extracts of cell wall-associated glycoproteins. In all species where oxidase activity was detected histochemically, it was expressed in cell walls of lignifying, differentiating xylem cells and was absent from old wood, cambium and phloem, suggesting that oxidases have a conservative role in lignification of tree xylem. An oxidase from the developing xylem of Picea sitchensis (Bong) Carr. (Sitka spruce) was partially purified by a combination of lectin affinity and immobilized metal ion affinity chromatography. A portion of the total oxidase activity had high affinity for immobilized zinc ions and this feature allowed it to be separated from the bulk of oxidase activity. Two polypeptides that could have been responsible for the bound oxidase activity were enriched by this procedure. The smaller polypeptide of Mr approximately 73 kDa yielded an N-terminal amino-acid sequence that was homologous to laccase-like polyphenol oxidases (E.C. 1.10.3.2) from loblolly pine (Pinus taeda L.), poplar (Populus euramericana (Dode) Guinier) and Arabidopsis. The larger polypeptide (Mr approximately 77 kDa) yielded an N-terminal amino-acid sequence that was homologous with a range of plant subtilisin-like serine proteinases. The roles of oxidase and proteinase activities in developing xylem are discussed.

Cycadopsida↗

Identification of a cis-acting replication element within the poliovirus coding region.

The replication of poliovirus, a positive-stranded RNA virus, requires translation of the infecting genome followed by virus-encoded VPg and 3D polymerase-primed synthesis of a negative-stranded template. RNA sequences involved in the latter process are poorly defined. Since many sequences involved in picornavirus replication form RNA structures, we searched the genome, other than the untranslated regions, for predicted local secondary structural elements and identified a 61-nucleotide (nt) stem-loop in the region encoding the 2C protein. Covariance analysis suggested the structure was well conserved in the Enterovirus genus of the Picornaviridae. Site-directed mutagenesis, disrupting the structure without affecting the 2C product, destroyed genome viability and suggested that the structure was required in the positive sense for function. Recovery of revertant viruses suggested that integrity of the structure was critical for function, and analysis of replication demonstrated that nonviable mutants did not synthesize negative strands. Our conclusion, that this RNA secondary structure constitutes a novel poliovirus cis-acting replication element (CRE), is supported by the demonstration that subgenomic replicons bearing lethal mutations in the native structure can be restored to replication competence by the addition of a second copy of the 61-nt wild-type sequence at another location within the genome. This poliovirus CRE functionally resembles an element identified in rhinovirus type 14 (K. L. McKnight and S. M. Lemon, RNA 4:1569-1584, 1998) and the cardioviruses (P. E. Lobert, N. Escriou, J. Ruelle, and T. Michiels, Proc. Natl. Acad. Sci. USA 96:11560-11565, 1999) but differs in sequence, structure, and location. The functional role and evolutionary significance of CREs in the replication of positive-sense RNA viruses is discussed.

Analysis of Variance↗

Functional consequences of a polymorphism affecting NF-kappaB p50-p50 binding to the TNF promoter region.

Stimulation of the NF-kappaB pathway often causes p65-p50 and p50-p50 dimers to be simultaneously present in the cell nucleus. A natural polymorphism at nucleotide -863 in the human TNF promoter (encoding tumor necrosis factor [TNF]) region provides an opportunity to dissect the functional interaction of p65-p50 and p50-p50 at a single NF-kappaB binding site. We found that this site normally binds both p65-p50 and p50-p50, but a single base change specifically inhibits p50-p50 binding. Reporter gene analysis in COS-7 cells expressing both p65-p50 and p50-p50 shows that the ability to bind p50-p50 reduces the enhancer effect of this NF-kappaB site. Using an adenoviral reporter assay, we found that the variant which binds p50-p50 results in a reduction of lipopolysaccharide-inducible gene expression in primary human monocytes. This finding adds to a growing body of experimental evidence that p50-p50 can inhibit the transactivating effects of p65-p50 and illustrates the potential for genetic modulation of inflammatory gene regulation in humans by subtle nucleotide changes that alter the relative binding affinities of different forms of the NF-kappaB complex.

Adenoviridae↗

Botulinum toxin (Dysport) treatment of hip adductor spasticity in multiple sclerosis: a prospective, randomised, double blind, placebo controlled, dose ranging study.

OBJECTIVE: To define a safe and effective dose of Dysport for treating hip adductor spasticity. METHODS: Patients with definite or probable multiple sclerosis, and disabling spasticity affecting the hip adductor muscles of both legs, were randomised to one of four treatment groups. Dysport (500, 1000, or 1500 Units), or placebo was administered by intramuscular injection to these muscles. Patients were assessed at entry, and 2, 4 (primary analysis time-point), 8, and 12 weeks post-treatment. RESULTS: A total of 74 patients were recruited. Treatment groups were generally well matched at entry. The primary efficacy variables-passive hip abduction and distance between the knees-improved for all groups. The improvement in distance between the knees for the 1500 Unit group was significantly greater than placebo (p = 0.02). Spasm frequency was reduced in all groups, but muscle tone was reduced in the Dysport groups only. Pain was reduced in all groups, but improvements in hygiene scores were evident only in the 1000 Unit and 1500 Unit groups. Duration of benefit was significantly longer than placebo for all Dysport groups (p<0.05). Adverse events were reported by 32/58 (55%) Dysport patients, and by 10/16 (63%) placebo patients. Compared with the two lower dose groups, twice as many adverse events were reported by the 1500 Unit group (2.7/patient). The incidence of muscle weakness was higher for the 1500 Unit group (36%) than for placebo (6%). The response to treatment was considered positive by two thirds of the patients in the 500 Unit group, and by about half the patients in the other groups. CONCLUSION: Dysport reduced the degree of hip adductor spasticity associated with multiple sclerosis, and this benefit was evident despite the concomitant use of oral antispasticity medication and analgesics. Although evidence for a dose response effect was not statistically significant, there was a clear trend towards greater efficacy and duration of effect with higher doses of Dysport. Dysport treatment was well tolerated, with no major side effects seen at doses up to 1500 Units. The optimal dose for hip adductor spasticity seems to be 500-1000 Units, divided between both legs.

Adult↗

Genetic analysis of bacteriophage-encoded cochaperonins.

Early genetic studies identified the Escherichia coli groES and groEL genes because mutations in them blocked the growth of bacteriophages lambda and T4. Subsequent genetic and biochemical analyses have shown that GroES and GroEL constitute a chaperonin machine, absolutely essential for E. coli growth, because it is needed for the correct folding of many of its proteins. In spite of very little sequence identity to GroES, the bacteriophage T4-encoded Gp31 protein and the bacteriophage RB49-encoded CocO protein are bona fide GroEL cochaperonins, even capable of substituting for GroES in E. coli growth. A major functional distinction is that only Gp31 and CocO can assist GroEL in the correct folding of Gp23, the major bacteriophage capsid protein. Conserved structural features between CocO and Gp31, which are absent from GroES, highlight their potential importance in specific cochaperonin function.

Bacterial Proteins↗