YhdP, TamB, and YdbH Are Redundant but Essential for Growth and Lipid Homeostasis of the Gram-Negative Outer Membrane
Natividad Ruiz, Rebecca M. Davis, Sujeet Kumar
Abstract
Gram-negative bacteria like Escherichia coli are characterized by having two membranes. Systems required for the biogenesis of the Gram-negative outer membrane have been identified except for that required for the transport of newly synthesized phospholipids from the inner to the outer membrane. The YhdP protein was previously implicated in this process. Here, we show that YhdP and its homologs TamB and YdbH are redundant in performing an essential function for growth and maintaining lipid homeostasis in the outer membrane. These proteins share a predicted structure with known eukaryotic lipid transporters. Based on our data and previous findings, we propose YhdP, TamB, and YdbH are the missing proteins that transport phospholipids to the outer membrane that have escaped identification because of redundancy.