title: Identification of a lexA gene in, and construction of a lexA mutant of, Xanthomonas campestris pv. citri.
abstract: The lexA gene of Xanthomonas campestris pathovar citri (X.c. pv. citri) was cloned and sequenced. The 639-bp open reading frame encodes a protein of 213 amino acids that shares substantial sequence homology with the products of previously characterized lexA genes, sharing 46% identity with the LexA protein of Escherichia coli. Amino acids required for autocatalytic cleavage of LexA are conserved in the X.c. pv. citri protein, whereas domains thought to mediate DNA binding differ markedly from those of LexA proteins from E. coli and other bacteria. The X.c. pv. citri LexA protein was overexpressed in E. coli, and SDS-polyacrylamide gel electrophoresis revealed a molecular size of 23 kDa for the purified protein. A lexA mutant of X.c. pv. citri was constructed by gene replacement, and the basal level of recA expression in this mutant was shown to be similar to that for wild-type cells exposed to a DNA-damaging agent. These results indicate that LexA functions as a repressor of recA expression in X.c. pv. citri.
authors.affiliation: Department of Biology, Fu Jen University, 510 Chun-Chen Road, Taipei 242, Taiwan, Republic of China.
authors.forename: M K
authors.initials: MK
authors.lastname: Yang
authors.forename: P I
authors.initials: PI
authors.lastname: Wu
authors.forename: Y C
authors.initials: YC
authors.lastname: Yang
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009154:Mutation; D011938:Rec A Recombinases / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology; D016959:Xanthomonas campestris / Q000737:chemistry / Q000235:genetics*; D000099160:LexA Repressor Protein
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D011938:Rec A Recombinases; D011994:Recombinant Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein