S. Calero et al., MOLECULAR-CLONING, SEQUENCE AND REGULATION OF EXPRESSION OF THE RECA GENE OF THE PHOTOTROPHIC BACTERIUM RHODOBACTER-SPHAEROIDES, MGG. Molecular & general genetics, 242(1), 1994, pp. 116-120
The recA gene of Rhodobacter sphaeroides 2.4.1 has been isolated by co
mplementation of a UV-sensitive RecA(-) mutant of Pseudomonas aerugino
sa. Its complete nucleotide sequence consists of 1032 bp, encoding a p
olypeptide of 343 amino acids. The deduced amino acid sequence display
ed highest identity to the RecA proteins from Rhizobium meliloti, Rhiz
obium phaseoli, and Agrobacterium tumefaciens. An Escherichia coli-lik
e SOS consensus region, which functions as a binding site for the LexA
repressor molecule was not present in the 215 bp upstream region of t
he R. sphaer oides recA gene. Nevertheless, by using a recA-lacZ fusio
n, we have shown that expression of the recA gene of R. sphaeroides is
inducible by DNA damage. A recA-defective strain of R. sphaeroides wa
s obtained by replacement of the active recA gene by a gene copy inact
ived in vitro. The resulting recA mutant exhibited increased sensitivi
ty to UV irradiation, and was impaired in its ability to perform homol
ogous recombination as well as to trigger DNA damage-mediated expressi
on. This is the first recA gene from a Gram-negative bacterium that la
cks an E. coli-like SOS box but whose expression has been shown to be
DNA damage-inducible and auto-regulated.