YajC, a predicted membrane protein, promotes biofilm formation and in a rat endocarditis model.

Biofilm formation is a critical step in the pathogenesis of difficult-to-treat Gram-positive bacterial infections. We identified that YajC, a conserved membrane protein in bacteria, plays a role in biofilm formation of the clinically relevant strain E1162. Deletion of conferred significantly impaired biofilm formation and was attenuated in a rat endocarditis model. Mass spectrometry analysis of supernatants of washed Δ cells revealed increased amounts in cytoplasmic and cell-surface-located proteins, including biofilm-associated proteins, suggesting that proteins on the surface of the mutant are only loosely attached. In YajC has been identified in complex with proteins of two cotranslational membrane protein-insertion pathways; the signal recognition particle (SRP)-SecYEG-YajC-YidC1 and the SRP-YajC-YidC2 pathway, but its function is unknown. In mutation of and resulted in impaired protein insertion in the cell membrane and secretion in the supernatant. The genome contains all homologous genes encoding for the cotranslational membrane protein-insertion pathways. By combining the studies in and , we propose that YajC is involved in the stabilization of the SRP-SecYEG-YajC-YidC1 and SRP-YajC-Yid2 pathway or plays a role in retaining proteins for proper docking to the YidC insertases for translocation in and over the membrane.