InterPro domain: IPR016467

The recA gene product is a multifunctional enzyme that plays a role in homologous recombination, DNA repair and induction of the SOS response [ 1 ]. In homologous recombination, the protein functions as a DNA-dependent ATPase, promoting synapsis, heteroduplex formation and strand exchange between homologous DNAs [ 2 ]. RecA also acts as a protease cofactor that promotes autodigestion of the lexA product and phage repressors. The proteolytic inactivation of the lexA repressor by an activated form of recA may cause a derepression of the 20 or so genes involved in the SOS response, which regulates DNA repair, induced mutagenesis, delayed cell division and prophage induction in response to DNA damage [ 2 ].

RecA is a protein of about 350 amino-acid residues. Its sequence is very well conserved [ 2 , 3 , 4 ] among eubacterial species. It is also found in the chloroplast of plants [ 5 ]. RecA-like proteins are found in archaea and diverse eukaryotic organisms, like fission yeast, mouse or human. In the filamentvisualised by X-ray crystallography, beta-strand 3, the loop C-terminal to beta-strand 2, and alpha-helix D of the core domain form one surface that packs against alpha-helix A and beta-strand 0 (the N-terminal domain) of an adjacent monomer during polymerisation [ 6 ]. The core ATP-binding site domain is well conserved, with 14 invariant residues. It contains the nucleotide binding loop between beta-strand 1 and alpha-helix C. The Escherichia coli sequence GPESSGKT matches the consensus sequence of amino acids (G/A)XXXXGK(T/S) for the Walker A box (alsoreferred to as the P-loop) found in a number of nucleoside triphosphate (NTP)-binding proteins. Anothernucleotide binding motif, the Walker B box is found at beta-strand 4 in the RecA structure. The Walker Bbox is characterised by four hydrophobic amino acids followed by an acidic residue (usually aspartate). Nucleotide specificity and additional ATP binding interactions are contributed by the amino acid residues at beta-strand 2 and the loop C-terminal to thatstrand, all of which are greater than 90% conserved among bacterial RecA proteins.

This entry represents a subset of the RecA-like proteins.

1. Characterization of recA genes and recA mutants of Rhizobium meliloti and Rhizobium leguminosarum biovar viciae. Mol. Gen. Genet. 229, 86-95
2. RecA protein: structure, function, and role in recombinational DNA repair. Prog. Nucleic Acid Res. Mol. Biol. 56, 129-223
3. Bacterial classifications derived from recA protein sequence comparisons. J. Bacteriol. 177, 6881-93
4. The RecA protein as a model molecule for molecular systematic studies of bacteria: comparison of trees of RecAs and 16S rRNAs from the same species. J. Mol. Evol. 41, 1105-23
5. A homolog of Escherichia coli RecA protein in plastids of higher plants. Proc. Natl. Acad. Sci. U.S.A. 89, 8068-72
6. The bacterial RecA protein and the recombinational DNA repair of stalled replication forks. Annu. Rev. Biochem. 71, 71-100