Use of recombinant DNA techniques to study DNA repair in Escherichia coli.
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Bacterial Proteins↗
Biomedical subjects
H M Arthur
Publications and source records attributed to H M Arthur.
The E. coli uvrD gene product is DNA helicase II.
We have shown that the uvrD gene product, previously identified in maxicell extracts as a 73 kilodalton protein, copurifies with single stranded DNA-dependent ATPase and ATP-dependent DNA helicase activities. This protein is specifically precipitated from maxicell extracts by antibodies raised against DNA helicase II. In order to facilitate purification of the UvrD protein we have subcloned the uvrD gene into a plasmid vector in which its transcription is under the control of the phage lambda leftward promoter. Using cells harbouring this recombinant plasmid as a source of elevated levels of the UvrD protein we have purified this protein to homogeneity by a simple, rapid procedure. The purified protein has single stranded DNA-dependent ATPase activity and ATP-dependent DNA helicase activity, and both activities are specifically inactivated by antibodies raised against DNA helicase II. We conclude that DNA helicase II is the uvrD gene product.
Adenosine Triphosphatases↗
Transcriptional control of the uvrD gene of Escherichia coli.
Transcription of the uvrD gene of Escherichia coli was studied using the Mud(Aprlac) gene fusion technique of Casadaban and Cohen [Proc. Natl. Acad. Sci. USA 76 (1979) 4530-4533]. Strains were isolated with Mud(Aprlac) inserted in both orientations and chromosome mobilisation experiments showed that transcription of uvrD was from ilvD towards metE. Constitutive expression of uvrD was approximately equivalent to 3000 protein molecules per cell. This level increased 1.5-fold following treatment with DNA damaging agents, an increase which was regulated by the recA and lexA genes. In addition, the constitutive expression of uvrD was reduced in strains containing either the recA56 mutation or a multi-copy plasmid carrying lexA+. These results indicate that uvrD is an SOS-inducible gene.
Bacterial Proteins↗
Cloning of the uvrD gene of E. coli and identification of the product.
The uvrD gene has been cloned from Escherichia coli chromosomal DNA into phage lambda, cosmid, and low-copy-number plasmid vectors. Comparison of the proteins encoded by the cloned fragments with those encoded by fragments in which the uvrD gene is inactivated by transposon insertion or by deletion shows that the uvrD gene product is a protein of Mr = 73000.
Bacteriophage lambda↗
Hyper-recombination in uvrD mutants of Escherichia coli K-12.
A mutant strain of E. coli which was isolated initially because of its strong hyper-recombination phenotype was shown to carry a lesion in uvrD. The presence of this mutation, designated uvrD210, increased the frequency of recombination between chromosomal duplications in F-prime repliconant cells and reduced linkage between closely linked markers in crosses with Hfr donors. A comparable hyper-rec phenotype was demonstrated in strains carrying other alleles of uvrD previously referred to as mutU4, uvr502 and recL152. The recombination activity of a uvrD210 strain was abolished by mutation of recA but the mutator activity associated with this allele proved to be independent of recA. It is suggested that uvrD mutations reduce the fidelity of DNA replication and that the accumulation of lesions in the newly synthesized strand provides additional sites for initiating recombination.
DNA Replication↗
Changes in exercise capacity and lipids after clinic versus home-based aerobic training in coronary artery bypass graft surgery patients.
PURPOSE: Despite the documented benefits of participating in rehabilitation programs, access to cardiac rehabilitation is limited for a large number of people with coronary artery disease (CAD). There is potential to increase participation in exercise training if home-based exercise were a viable option. METHODS: We conducted a retrospective database review of 1,042 patients who took part in exercise rehabilitation following coronary artery bypass graft surgery (CABGS) between 1992 and 1998. Of these, 713 patients took part in supervised exercise, and 329 were in an unsupervised, home-based group. All exercise protocols were based upon American College of Sports Medicine guidelines, and patients in both groups received exercise prescriptions that were similar in intensity, frequency, and duration. RESULTS: There were no differences between groups at baseline. Following 6 months of exercise training, there were substantial improvements in peak VO2, peak workload, and peak MET levels in both the supervised and unsupervised groups (P < 0.0001). Patients in the supervised group had significant improvements in both LDL and HDL-cholesterol, whereas the home-based group showed improvement in HDL-cholesterol only. When analyzed by sex, men performed better than women for all measures of exercise capacity; however, women in both groups showed approximate 20% improvements (P < 0.05) in exercise capacity as well as improvements in HDL-cholesterol. CONCLUSION: Stable post CABGS patients who receive a detailed exercise prescription to follow at home do as well as those in supervised rehabilitation.
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