The function of the cell membrane is to maintain conditions inside the cell that differ from the outer environment. Integral to the emergence of life, the critical role of a ‘sealed membrane’ has led to the evolution of mechanisms to protect it from damaging stresses. However, while there is evidence of cellular repair systems, little is known about how these protection systems work.

A key member is an ancient family of proteins called IM30 proteins. IM30 proteins were first recognised as PspA in bacteria and have subsequently been recognised as VIPP1 proteins in cyanobacteria and plants. In addition, they are structurally analogous to mammalian ESCRT-III proteins.

As a component of a larger collaborative project, my research focuses on two IM30 proteins found in the bacterium Bacillus subtilis, PspA and LiaH. Expression of these proteins is induced upon membrane stress, and we have discovered a functional role for LiaH in rescuing membrane function. In addition, we have identified an additional potential IM30-like protein, YvlB, in B. subtilis. This is significant as it shares sequence homology with LiaX, a key protein in the membrane stress response in the bacterial pathogen Enterococcus faecalis, which notably does not encode a canonical IM30 protein.

Using a combination of molecular genetics, antimicrobial susceptibility assays and fluorescence microscopy I will discuss how we are beginning to understand the functional role of these proteins in response to membrane stress and to identify key components integral to their function.