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Inhibitory effect of alpha 2-macroglobulin on Vibrio vulnificus protease
Abstract:
Vibrio vulnificus, an etiologic agent of wound infections and septicemia in humans, elaborates a metalloprotease which is known to be an important virulence factor of the Vibrio. The proteolytic activity of V. vulnificus metalloprotease (VVP) toward casein and elastin was inhibited by alpha 2-macroglobulin (alpha 2 M) at the molar ratio of 1:1, although partial activity was maintained. Permeability-enhancing and hemorrhagic activities were also inhibited, but the peptidase activity toward Z-Gly-Phe-NH2 was not reduced, even by an excess amount of alpha 2 M. VVP formed a complex with alpha 2 M through cleavage of the bait regions of all four alpha 2 M subunits and elicitation of conformational change of the alpha 2 M molecule, which resulted in entrapment of VVP in the alpha 2 M molecule. The peptidase activity of alpha 2 M-VVP complex was inhibited by low-molecular-weight inhibitors such as phosphoramidon, but IgG antibody against VVP failed to neutralize its peptidase activity. Of human plasma proteins, alpha 2 M was the only inhibitor for VVP. These findings indicate that VVP produced during V. vulnificus infection is inactivated by plasma alpha 2 M that leaks from the vascular system.
Insights
Vibrio vulnificus metalloprotease (VVP), a key virulence factor, is inactivated by human plasma alpha 2-macroglobulin (alpha 2 M). This interaction neutralizes VVP
Area of Science:
- Microbiology
- Biochemistry
- Immunology
Background:
- Vibrio vulnificus causes severe human infections.
- V. vulnificus metalloprotease (VVP) is a crucial virulence factor.
- Understanding VVP's interaction with host proteins is vital for therapeutic strategies.
Purpose of the Study:
- To investigate the inhibitory effects of human plasma proteins on V. vulnificus metalloprotease (VVP).
- To elucidate the mechanism of interaction between VVP and alpha 2-macroglobulin (alpha 2 M).
Main Methods:
- Protease activity assays using casein and elastin.
- Inhibition assays with human plasma proteins, including alpha 2 M.
- Analysis of VVP-alpha 2 M complex formation and activity.
- Testing inhibition by low-molecular-weight inhibitors and antibodies.
Main Results:
- Alpha 2-macroglobulin (alpha 2 M) inhibited VVP's proteolytic, permeability-enhancing, and hemorrhagic activities.
- VVP formed a stable complex with alpha 2 M via cleavage of its bait regions.
- The peptidase activity of VVP toward Z-Gly-Phe-NH2 was not inhibited by alpha 2 M.
- Low-molecular-weight inhibitors, but not IgG antibodies, inhibited the alpha 2 M-VVP complex activity.
- Alpha 2 M was the sole inhibitor among tested human plasma proteins.
Conclusions:
- Plasma alpha 2-macroglobulin effectively inactivates V. vulnificus metalloprotease (VVP) during infection.
- The interaction involves complex formation and conformational changes in alpha 2 M.
- VVP's specific peptidase activity may remain despite alpha 2 M binding, suggesting potential for residual pathogenicity.