Natividad Ruiz, Professor, Department of Microbiology, The Ohio State University, will give a talk on "Lipid transporters that build the outer membrane of Gram-negative bacteria."

***This seminar will be in-person ONLY. There will be NO Zoom broadcast***

ABSTRACT

Gram-negative bacteria have a multi-layered envelope that is delimited by two membranes. The inner membrane, which surrounds the cytoplasm, is a phospholipid bilayer, while the outer membrane contains phospholipids in its inner leaflet and lipopolysaccharides (LPS) in its outer leaflet. Since lipids are synthesized at the inner membrane, they must be transported across the cell envelope to build the outer membrane. For almost two decades, we have known that the multi-protein Lpt system forms an inter-membrane bridge that transports LPS to the cell surface. How phospholipids are shuttled to the outer membrane had been elusive until recently. We proposed that three functionally redundant AsmA-like protein paralogs (TamB, YhdP, and YdbH) transport phospholipids to the outer membrane of Escherichia coli. AsmA-like proteins are the bacterial ancestors of the eukaryotic proteins containing RBG (repeating β-groove) domains that mediate bulk lipid transport between organelles; they are predicted to form bridge-like structures that provide a long hydrophobic groove that shields acyl chains from the aqueous periplasmic compartment as they travel to the outer membrane. Recently, we have identified functional partners of YdbH. Our data show that YdbH is anchored to the inner membrane and interacts with the outer membrane lipoprotein YnbE to form a structure that bridges the inner and outer membranes. We also propose that the periplasmic protein YdbL participates in the biogenesis of the YdbH-YnbE complex.