Modulation of Vibrio mimicus hemolysin through limited proteolysis by an endogenous metalloprotease

Abstract

Vibrio mimicus is a causative agent of human gastroenteritis and food poisoning, and this species produces an enterotoxic hemolysin (V. mimicus hemolysin) as a virulence determinant. Vibrio mimicus hemolysin is secreted as an 80 kDa precursor, which is later converted to the 66 kDa mature toxin through removal of an N‐terminal propeptide via cleavage of the Arg151–Ser152 bond. In this article, we investigate the role of the endogenous metalloprotease (V. mimicus protease) in the maturation of V. mimicus hemolysin. In vitro experiments using purified proteins showed that, although it activated the precursor at the early stage via cleavage of the Asn157–Val158 bond, V. mimicus protease finally converted the activated and physiologically maturated toxin to a 51 kDa protein through removal of the C‐terminal polypeptide. This 51 kDa derivative was unable to lyse erythrocytes because of its inability to bind to the erythrocyte membrane. Vibrio mimicus protease‐negative strains were found to produce high levels of V. mimicus hemolysin at the logarithmic phase of bacterial growth and maintained high hemolytic activity even at the stationary phase. These findings indicate that, although it is not directly related to toxin maturation in vivo, V. mimicus protease can modulate the activity of V. mimicus hemolysin and/or its precursor through limited proteolysis.

Quorum Sensing Negatively Regulates Hemolysin Transcriptionally and Posttranslationally in Vibrio cholerae

“…Previous studies of a related species, V. vulnificus, have indicated that a metalloprotease, VvpE, may inactivate a hemolysin, VvhA, but there have been conflicting reports (34,35). Studies of V. mimicus and V. tubiashii have also shown a similar relationship between a protease and a hemolysin (14,27). In V. cholerae, HapR increases the expression levels of two genes encoding metalloproteases, hapA and prtV (17,46).…”

“…on May 12, 2018 by guest http://iai.asm.org/ true that deletion of the protease gene resulted in higher rather than lower levels of hemolytic activity, so it was concluded that that metalloprotease is not responsible for proper processing of the hemolysin and in fact leads to degradation of the hemolysin (27). In addition to repressing HlyA activity through HapA, we show that HapR also represses transcription from the hlyA promoter directly.…”

Presence of the Hemolysin Gene of Vibrio mimicus in Fish and Seafood Products in Sonora, Mexico

“…mimicus produces several extracellular toxic factors, but the most common factor is a heat-labile hemolytic/cytolytic toxin known as V. mimicus hemolysin or VHM (Mizuno et al, 2009;Mizuno, Nanko, Maehara, Shinoda, & Miyoshi, 2014). The VHM gene, vmh, is common to clinical and environmental V. mimicus strains, and it is a species-specific identifier (Shinoda et al, 2004;Sultan et al, 2007).…”

A novel extracellular protease of Vibrio mimicus that mediates maturation of an endogenous hemolysin

“…However, the proteolytic enzyme that mediates maturation of VMH has not been identified. Recently, a metalloprotease from V. mimicus was found to have the potential to activate pro‐VMH by hydrolysis of the Asn 157 Val 158 bond . However, the main action of the metalloprotease was clarified as inactivation of VMH by digestion of the C‐terminal 15 kDa polypeptide .…”

“…Recently, a metalloprotease from V. mimicus was found to have the potential to activate pro‐VMH by hydrolysis of the Asn 157 Val 158 bond . However, the main action of the metalloprotease was clarified as inactivation of VMH by digestion of the C‐terminal 15 kDa polypeptide . Interestingly, it was also found that sufficient amounts of mature VMH accumulate in culture supernatants of the metalloprotease‐negative mutant .…”