Sequence and functional analysis of the gene encoding Vibrio cholerae cAMP receptor protein

We describe here the cloning, nucleotide sequence, and functional expression of the crp gene of Vibrio cholerae (Vc) encoding the cyclic AMP receptor protein (CRP). The Vc crp gene shows 81% identity with the crp gene from Escherichia coli (Ec) and its deduced amino acid sequence shows 95% identity with the Ec protein. When expressed from inducible promoters, the cloned Vc gene produced an approximately 20-kDa protein which complemented the carbohydrate-negative and growth-defective phenotypes of both Ec and Vc crp mutants. In the Vc crp mutant, the cloned crp gene also restored the normal repression of ToxR-regulated virulence genes which occurs under certain environmental conditions.