Structural Analysis of YhdP Reveals Important Regions for the Stability and Function of the Protein in Membrane Biogenesis

Abstract

Cell membranes play essential roles in structure, protection from the environment, and transport regulation. Thus, they are essential in the maintenance of homeostasis for cells and are essential for understanding physiology. For bacteria, like Escherichia coli, which are often found in hostile environments, the role of the cell envelope and its maintenance is especially critical. The envelope consists of an inner membrane, an outer membrane, and a peptidoglycan layer in the space between the two membranes. The outer membrane consists of lipopolysaccharide on the outer leaflet and phospholipids on the inner leaflet. However, these lipids are synthesized in the cytosol or inner membrane and need to be transported to their final cellular location. Although transporters for many of the essential components for membrane biogenesis have been identified and characterized, transport of phospholipids is not well understood. It is hypothesized that TamB, YhdP, and YdbH are redundantly involved in transport of PLs. Out of the three, YhdP remains the least understood. By using site-directed mutagenesis to introduce mutations throughout the protein, this study has shown that there are several regions of the protein that are important for protein function. Of importance, this study has identified YhdP with L1134C and A1197C which creates an inactive confirmation of the protein and requires further examination. Furthermore, many mutations that destabilize the protein have also been identified, raising the question of the tolerance of the protein to mutations.