Stress-Responsive Periplasmic Chaperones in Bacteria.

Hyunhee Kim,Kevin Wu,Changhan Lee

doi:10.3389/fmolb.2021.678697

Abstract

Periplasmic proteins are involved in a wide range of bacterial functions, including motility, biofilm formation, sensing environmental cues, and small-molecule transport. In addition, a wide range of outer membrane proteins and proteins that are secreted into the media must travel through the periplasm to reach their final destinations. Since the porous outer membrane allows for the free diffusion of small molecules, periplasmic proteins and those that travel through this compartment are more vulnerable to external environmental changes, including those that result in protein unfolding, than cytoplasmic proteins are. To enable bacterial survival under various stress conditions, a robust protein quality control system is required in the periplasm. In this review, we focus on several periplasmic chaperones that are stress responsive, including Spy, which responds to envelope-stress, DegP, which responds to temperature to modulate chaperone/protease activity, HdeA and HdeB, which respond to acid stress, and UgpB, which functions as a bile-responsive chaperone.

Highlights

Proteins are involved in various cellular pathways, such as replication of DNA, gene regulation and metabolism, in all living organisms
The periplasmic chaperones SurA and DegP have been implicated as HdeA substrates under low-pH conditions (Zhang et al, 2011), and HdeA suppresses the acid-induced aggregation of SurA in vitro (Zhang et al, 2011)
Many cytosolic chaperones utilize ATP to modulate their activity, but periplasmic chaperones require an alternative regulatory mechanism because the periplasmic space is completely lacking in ATP

Summary

Introduction

Proteins are involved in various cellular pathways, such as replication of DNA, gene regulation and metabolism, in all living organisms. We have chosen to focus on the periplasmic chaperones which are regulated at the post-translation level by environmental stresses such as the temperature-responsive chaperone/protease DegP; the acid-responsive chaperone, HdeA and HdeB; and the bile-responsive chaperone, UgpB. HdeA and HdeB appear to utilize changes in external pH to trigger chaperone activation, inactivation, and substrate-protein refolding (Figure 3A).

Results

Conclusion