Two forms of Vibrio vulnificus metalloprotease VvpE are secreted via the type II general secretion system

Abstract

Vibrio vulnificus has been known to secrete one form of metalloprotease VvpE (45 kDa) that is cleaved to 34 kDa-VvpE and 11 kDa-C-terminal propeptide via extracellular autoproteolysis. However, we found that extracellular secretion of both the 34 and 45 kDa forms of VvpE began in the early growth phase; moreover, 34 kDa-VvpE existed as the major form in V. vulnificus cell lysates and culture supernatants. In addition, extracellular secretion of both 34 and 45 kDa-VvpE was blocked by mutation of the pilD gene, which encodes for the type IV leader peptidase/N-methyltransferase of the type II general secretion system, and the blocked VvpE secretion was recovered by in trans-complementation of the wild-type pilD gene. These results indicate that 34 kDa-VvpE is the major form secreted along with 45 kDa-VvpE from the early growth phase via the PilD-mediated type II general secretion system.