Linked Life Data

2002048

Source:http://linkedlifedata.com/resource/pubmed/id/2002048

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
8
pubmed:dateCreated
1991-4-17
pubmed:abstractText
Most potent mutators heretofore detected in Escherichia coli are associated with defects in epsilon subunit of DNA polymerase III, encoded by the dnaQ gene. To elucidate the role of the alpha subunit, the catalytic subunit of the polymerase, in maintaining the high fidelity of DNA replication, we isolated a mutator mutant, the mutation (dnaE173) of which resides on the dnaE gene, encoding the alpha subunit. The dnaE173 mutant was unable to grow in salt-free L broth at temperatures exceeding 44.5 degrees C and exhibited an increased frequency of spontaneous mutations, 1,000 to 10,000-fold the wild type level, at permissive temperatures. The mutator effect of dnaE173 mutation is dominant over the wild type allele. These phenotypes are caused by a single base substitution, resulting in one amino acid change, Glu612 (GAA)----Lys(AAA), in the alpha subunit molecule. DNA polymerase III purified from the dnaE173 mutant contained both alpha and epsilon subunits, in a normal molar ratio. We found no differences between wild type and mutant polymerases in the Vmax, thermolabilities, and salt sensitivities. However, the apparent Km for the substrate nucleotide of the mutant polymerase was 1/6 of that determined with the wild type polymerase. Although the mutant polymerase retained a normal level of 3'----5' exonuclease activity, the proofreading capacity determined by "turnover assay" was significantly lower in the mutant polymerase, as compared with findings in the normal enzyme. It seems likely that the enhanced mutability in the dnaE173 strain results from, at least in part, a defect in the editing function of DNA polymerase III, and further suggests that a portion of the alpha subunit in which the amino acid change resides may be important for the proper setting of the two subunits at the replication fork so as to facilitate efficient editing during the DNA replication.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
15
pubmed:volume
266
pubmed:geneSymbol
dnaE, dnaQ
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
5055-61
pubmed:dateRevised
2010-11-18
pubmed:meshHeading
pubmed:year
1991
pubmed:articleTitle
A strong mutator effect caused by an amino acid change in the alpha subunit of DNA polymerase III of Escherichia coli.
pubmed:affiliation
Department of Biochemistry, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
pubmed:publicationType
Journal Article, Research Support, Non-U.S. Gov't