Bright fluorescence of a novel protein from Vibrio vulnificus depends on NADPH and the expression of this protein is regulated by a LysR-type regulatory gene.

A blue fluorescent protein, BfgV, belonging to the short-chain dehydrogenase/reductase superfamily, was found in a non-bioluminescent pathogen Vibrio vulnificus CKM-1. This protein has fluorescence spectra with two excitation peaks at 283 and 352 nm, and one emission peak at 456 nm. BfgV fluoresces through effectively augmenting the intrinsic fluorescence of NADPH bound to it. Escherichia coli transformants expressing this protein can emit eye-detectable fluorescence. A LysR-type transcriptional regulator gene bfgR was found at the vicinal upstream region of bfgV in CKM-1 genome. The clues that products of bfgR can specifically bind to bfgR-bfgV intergenic promoter region and the deletion of bfgR significantly decreases the expression of bfgV reveal bfgR is a repressor gene of bfgV in V. vulnificus CKM-1.