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

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Protein Secretion

Background:

• Vibrio vulnificus metalloprotease VvpE (45 kDa) is typically cleaved into 34 kDa-VvpE and an 11 kDa C-terminal propeptide via extracellular autoproteolysis.
• Previous understanding focused on the mature VvpE form after autoproteolytic cleavage.

Purpose of the Study:

• To investigate the secretion dynamics and forms of VvpE in Vibrio vulnificus.
• To elucidate the role of the type II general secretion system in VvpE secretion.

Main Methods:

• Analysis of VvpE forms in V. vulnificus cell lysates and culture supernatants during early growth phases.
• Genetic manipulation, including pilD gene mutation and in trans-complementation, to assess secretion pathways.
• Characterization of VvpE secretion in wild-type and mutant strains.

Main Results:

• Extracellular secretion of both 34 kDa and 45 kDa VvpE forms was observed starting in the early growth phase.
• The 34 kDa form of VvpE was identified as the predominant form in both cell lysates and culture supernatants.
• Mutation of the pilD gene, encoding a key component of the type II general secretion system, abolished VvpE secretion.
• Complementation with the wild-type pilD gene restored VvpE secretion, confirming the system's involvement.

Conclusions:

• The 34 kDa VvpE is the major secreted form of metalloprotease in V. vulnificus, secreted alongside the 45 kDa form.
• Secretion of both VvpE forms initiates early in the growth phase.
• The PilD-mediated type II general secretion system is essential for the extracellular secretion of VvpE in V. vulnificus.