Role of a Highly Conserved Bacterial Protein in Outer Membrane Protein Assembly

TLDR

Bacterial outer membrane proteins are assembled into the outer membrane after cytoplasmic transport, and the highly conserved Omp85 protein (with chloroplast homolog Toc75) is implicated in this process. Omp85 depletion leads to accumulation of unassembled outer membrane proteins, reduced surface exposure especially at division planes, confirming its essential role in outer membrane protein assembly.

Abstract

After transport across the cytoplasmic membrane, bacterial outer membrane proteins are assembled into the outer membrane. Meningococcal Omp85 is a highly conserved protein in Gram-negative bacteria, and its homolog Toc75 is a component of the chloroplast protein-import machinery. Omp85 appeared to be essential for viability, and unassembled forms of various outer membrane proteins accumulated upon Omp85 depletion. Immunofluorescence microscopy revealed decreased surface exposure of outer membrane proteins, which was particularly apparent at the cell-division planes. Thus, Omp85 is likely to play a role in outer membrane protein assembly.