title: Nucleotide sequence of the Escherichia coli micA gene required for A/G-specific mismatch repair: identity of micA and mutY.
abstract: The Escherichia coli methylation-independent repair pathway specific for A/G mismatches has been shown to require the gene product of micA. Extracts prepared from micA mutants do not form an A/G mismatch-specific DNA-protein complex and do not contain an A/G mismatch-specific nicking activity. Moreover, a partially purified protein fraction containing both A/G mismatch-specific nicking and binding activities restores repair activity in micA mutant extracts. The DNA sequence of a 2.3-kb fragment containing the micA gene has been determined. There are two open reading frames (ORF) in this DNA fragment: one ORF encodes a 25.7-kDa protein whose function is still unknown, the other ORF codes for a protein with an Mr of 39,147, but this ORF can be transcribed and the mRNA can be translated to yield a protein with an apparent Mr of 36 kDa on a sodium dodecyl sulfate-polyacrylamide gel. Deletion analysis showed that this 39.1-kDa ORF is the micA gene as judged by the capacity of the encoded protein to restore the A/G mismatch-specific nicking activity of micA mutant extracts. Furthermore, our results suggest that micA is the same gene as the closely mapped mutY, which encodes the A/G mismatch-specific glycosylase.
authors.affiliation: Department of Biological Chemistry, School of Medicine, University of Maryland, Baltimore 21201.
authors.forename: J J
authors.initials: JJ
authors.lastname: Tsai-Wu
authors.forename: J P
authors.initials: JP
authors.lastname: Radicella
authors.forename: A L
authors.initials: AL
authors.lastname: Lu
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D045647:DNA Glycosylases; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics*; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009154:Mutation; D009699:N-Glycosyl Hydrolases / Q000235:genetics*; D015183:Restriction Mapping; D013379:Substrate Specificity
chemical_list: D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases