An Stomatin, Prohibitin, Flotillin, and HflK/C-Domain Protein Required to Link the Phage-Shock Protein to the Membrane in Bacillus subtilis.

Diana Wolf,Abigail Savietto Scholz,Sarah S M Baur,Marc Bramkamp

doi:10.3389/fmicb.2021.754924

Abstract

Membrane surveillance and repair is of utmost importance to maintain cellular integrity and allow cellular life. Several systems detect cell envelope stress caused by antimicrobial compounds and abiotic stresses such as solvents, pH-changes and temperature in bacteria. Proteins containing an Stomatin, Prohibitin, Flotillin, and HflK/C (SPFH)-domain, including bacterial flotillins have been shown to be involved in membrane protection and membrane fluidity regulation. Here, we characterize a bacterial SPFH-domain protein, YdjI that is part of a stress induced complex in Bacillus subtilis. We show that YdjI is required to localize the ESCRT-III homolog PspA to the membrane with the help of two membrane integral proteins, YdjG/H. In contrast to classical flotillins, YdjI resides in fluid membrane regions and does not enrich in detergent resistant membrane fractions. However, similarly to FloA and FloT from B. subtilis, deletion of YdjI decreases membrane fluidity. Our data reveal a hardwired connection between phage shock response and SPFH proteins.

Highlights

All living cells are surrounded by a membrane barrier that shields them from the outside environment
B. subtilis encodes a third SPFHdomain protein, YdjI that is encoded in the pspA-ydjGHI operon (Popp et al, 2021; Ravi et al, 2021)
The first protein encoded in the operon, PspA, is another ubiquitously found protein that is involved in cell envelope stress response

Summary

Introduction

All living cells are surrounded by a membrane barrier that shields them from the outside environment. The cell membrane is a dynamic structure containing a lipid bilayer with membrane integral and associated proteins. In the model-organism Bacillus subtilis, phospholipids such as the neutral lipid phosphatidylethanolamine, the anionic phospholipids phosphatidylglycerol and cardiolipin are the major lipid species in the cell membrane (Nickels et al, 2017), while the membrane proteome comprises proteins with several different functions such as membrane synthesis, remodeling, energy metabolism, as well as transport and signaling. Membrane regions with altered lipid composition and ordering are associated with the generation of micro-heterogenous domains referred to as lipid rafts or functional membrane microdomains (FMMs) (Simons and Ikonen, 1997; Jacobson et al, 2007).

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