4b54
The Structure of the inactive mutant G153R of LptC from E. coli
Structural highlights
FunctionLPTC_ECOLI Required for the translocation of lipopolysaccharide (LPS) from the inner membrane to the outer membrane. It facilitates the transfer of LPS from the inner membrane to a periplasmic chaperone, LptA.[1] [2] [3] Publication Abstract from PubMedLipopolysaccharide is a major glycolipid component in the outer leaflet of outer membrane, a peculiar permeability barrier of Gram-negative bacteria that prevents many toxic compounds from entering the cell. Lipopolysaccharide transport across the periplasmic space and its assembly at the Escherichia coli cell surface are carried over by a transenvelope complex of seven essential lipopolysaccharide transport(Lpt) proteins spanning the inner membrane (LptBCFG), the periplasm (LptA), and the OM (LptDE), which appears to operate as a unique machinery.LptC is an essential inner membrane-anchored protein with a large periplasm-protruding domain. LptC binds the inner membrane LptBFG ABC transporter and interacts with the periplasmic protein LptA. However its role in Lipopolysaccharide transport is unclear.Here we show that LptC lacking the transmembrane region is viable and can bind the LptBFG inner membrane complex; thus the essential LptC functions are located in the periplasmic domain. In addition, we characterize two previously described inactive single mutants at two conserved glycines (G56V and G153R, respectively) of the LptC periplasmic domain, showing that neither mutant is able to assemble the transenvelope machinery. However, while LptCG56V failed to co-purify any Lpt component, LptCG153R was able to interact with the inner membrane protein complex LptBFG.Overall, our data further support the model whereby the bridge connecting inner and outer membrane would be based on the conserved structurally homologous jellyroll domain shared by five out of the seven Lpt components. The Escherichia coli Lpt transenvelope protein complex for lipopolysaccharide export is assembled via conserved structurally homologous domains.,Villa R, Martorana AM, Okuda S, Gourlay LJ, Nardini M, Sperandeo P, Deho G, Bolognesi M, Kahne D, Polissi A J Bacteriol. 2013 Jan 4. PMID:23292770[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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