The cytolysin gene of Vibrio vulnificus: sequence and relationship to the Vibrio cholerae E1 Tor hemolysin gene

Abstract

A cytolysin of ca. 56 kilodaltons has been suggested as a possible virulence factor in Vibrio vulnificus infections. We sequenced the DNA encoding cytolytic activity and found that the sequence contained two open reading frames, vvhA and vvhB. vvhA encoded the structural gene for the cytolysin and contained the N-terminal amino acid sequence previously reported for the protein. Regions of the vvhA gene showed homology to the structural gene for the Vibrio cholerae El Tor hemolysin.

Haemolysins in Vibrio species

“…V. mimicus, V. vulnificus, V. anguillarum and V. fluvialis) produce haemolysins, which share common features with HlyA haemolysin (e.g. Ichinose et al 1987;Yamamoto et al 1990b;Hirono et al 1996;Ikigai et al 1996;Kim et al 1997;Rahman et al 1997;Choi et al 2002;Han et al 2002;Kothary et al 2003). For example, the structural gene (vmhA) of the haemolysin from V. mimicus (VMH) was cloned, and the nucleotide sequence was determined (Kim et al 1997;Rahman et al 1997).…”

“…Most of the clinical and environmental V. mimicus isolates examined were shown to possess the vmh gene (Shi et al 2000;Shinoda et al 2004). Similarly, regions of the structural gene (vvhA) of V. vulnificus haemolysin (VVH) resembled the corresponding gene of HlyA haemolysin, both in terms of sequence and organization (Yamamoto et al 1990b;Choi et al 2002). VVH, of which the purified molecule had a molecular mass of 51 kDa, lysed erythrocytes from a variety of animal species by forming small pores in the cytoplasmic membrane (Yamamoto et al 1990b).…”

“…Similarly, regions of the structural gene (vvhA) of V. vulnificus haemolysin (VVH) resembled the corresponding gene of HlyA haemolysin, both in terms of sequence and organization (Yamamoto et al 1990b;Choi et al 2002). VVH, of which the purified molecule had a molecular mass of 51 kDa, lysed erythrocytes from a variety of animal species by forming small pores in the cytoplasmic membrane (Yamamoto et al 1990b). Interestingly, production of VVH in V. vulnificus was repressed by the addition of glucose to the culture media; expression being depressed by cAMP, which suggested that haemolysin synthesis is regulated by cAMP-CRP (cAMP receptor protein) controlled catabolite repression (Bang et al 1999).…”

“…An extracellular cytolysin from V. tubiashii, a pathogen which causes bacillary necrosis in larval and juvenile bivalve (Tubiash et al 1970), was purified (Kothary et al 2001). Twelve of the first 17 N-terminal amino acid residues are identical to those of the V. vulnificus VVH (Yamamoto et al 1990b;Kothary et al 2001). Moreover, this cytolysin, which is sensitive to heat and proteases and is inhibited by cholesterol, has a molecular weight of 59 kDa (Kothary et al 2001).…”

“…In addition to the vvhA haemolysin gene (Yamamoto et al 1990b;Choi et al 2002), another haemolysin gene (vllY) from V. vulnificus has been identified (Chang et al 1997). Nucleotide sequence analysis predicted an ORF of 1071 bp, encoding a 357 amino acid polypeptide with an estimated pI of 5AE02 (Chang et al 1997).…”