Investigating the role of YhdP and other AsmA-like proteins in phospholipid transport in gram-negative bacteria

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Gram-negative bacteria have an elevated resistance to current antibiotics due to the sophisticated architecture of their outer membrane. This membrane acts as an impermeable barrier to hydrophilic molecules and small hydrophobic molecules including antibiotics and detergents. The asymmetric outer membrane is composed of phospholipids and LPS in the inner and outer leaflets respectively, and whilst understanding of LPS synthesis and transport is well understood, the movement of phospholipids between the membranes is surprisingly unknown. Recently, the inner membrane protein YhdP has been implicated in high-flux phospholipid transport, having been shown to delay the cell death phenotype of MlaA* mutants, a mutant that causes inner membrane rupture by disrupting the maintenance of lipid asymmetry (Mla) pathway. Additionally, E. coli cells with a yhdP deletion have a weaker outer membrane and increased sensitivity to SDS+EDTA and vancomycin. YhdP is a member of the AsmA-like family of proteins, sharing a common AsmA-like domain, and so may share similar functions. The project will investigate YhdP and the other AsmA-like proteins, namely AsmA, TamB, YhjG, YicH and YdbH, to determine their role in outer membrane biogenesis in gram-negative bacteria. A multidisciplinary approach involving biochemistry, biophysics and molecular biology techniques will be used, including X-ray crystallography, neutron reflectometry and cryo-electron microscopy. This project will contribute to our existing knowledge of this enigmatic process and may lead to the discovery of novel antibiotic targets to combat the public health threat of rising antimicrobial resistance.