Functional Study of YjfN as an Activator of DegP Protease

Abstract

DegP protease is a major constituent of protein quality control in the periplasm of Gram-negative bacteria. DegP performs regulated proteolysis of misfolded or aggregated proteins, and the function of DegP is essential for the survival of Gram-negative bacteria at high temperature. DegP shows distinct features of activity regulation compared to the cytoplasmic proteases, and it is still unknown that whether any native proteins can regulate DegP activity. In this study, we report the functions of YjfN, a previously unknown periplasmic protein. We found that it functions as a substrate of DegP. Interestingly, during its degradation, YjfN induces activation of DegP in trans. Various features of YjfN indicate that YjfN activates DegP to relieve envelope stress. To our knowledge, this is the first protein which works as a suicide activator. Our findings suggest another possible strategy of enzyme activity regulation.