Cloning, sequence and regulation of expression of the lexA gene of Aeromonas hydrophila.
The lexA gene of Aeromonas hydrophila (Ah) has been isolated by using a specific one-step cloning system. The Ah LexA repressor is able to block Escherichia coli (Ec) SOS gene expression and is likely to be cleaved by the activated RecA protein of this bacterial species after DNA damage. Ah lexA would encode a protein of 207 amino acids (aa), which is 75% identical to the LexA repressor of Ec. Two Ec-like SOS boxes have been located upstream from Ah lexA, the distance between them being 4 bp, whereas this same distance in Ec lexA is 5 bp. The structure and sequence of the DNA-binding domain of the LexA repressor of Ec, as well as the region at which its hydrolysis occurs, are highly conserved in Ah LexA. Moreover, a residue of the region implicated in the specific cleavage reaction, and which is present in all known RecA-cleavable repressors, is changed in the Ah LexA. Expression of Ah lexA is DNA-damage inducible in both the Ah and Ec genetic backgrounds to the same extent. In contrast, Ec lexA is poorly induced in DNA-injured Ah cells.
Riera
J
J
Department of Genetics and Microbiology, Autonomous University of Barcelona, Spain.
Barbé
J
J
D016980:Aeromonas hydrophila / Q000235:genetics*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D011938:Rec A Recombinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013014:SOS Response, Genetics; D016415:Sequence Alignment; D017385:Sequence Homology; D012697:Serine Endopeptidases; D013045:Species Specificity; D000099160:LexA Repressor Protein
D001426:Bacterial Proteins; D011938:Rec A Recombinases; D011993:Recombinant Fusion Proteins; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein