4B54: The Structure Of The Inactive Mutant G153r Of Lptc From E.coli

Citation:
Abstract
Lipopolysaccharide is a major glycolipid component in the outer leaflet of the outer membrane (OM), a peculiar permeability barrier of Gram-negative bacteria that prevents many toxic compounds from entering the cell. Lipopolysaccharide transport (Lpt) across the periplasmic space and its assembly at the Escherichia coli cell surface are carried out by a transenvelope complex of seven essential 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 mutations 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 copurify 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 the inner and outer membranes would be based on the conserved structurally homologous jellyroll domain shared by five out of the seven Lpt components.
PDB ID: 4B54Download
MMDB ID: 106669
PDB Deposition Date: 2012/8/2
Updated in MMDB: 2013/02
Experimental Method:
x-ray diffraction
Resolution: 2.8  Å
Source Organism:
Similar Structures:
Biological Unit for 4B54: dimeric; determined by author and by software (PISA)
Molecular Components in 4B54
Label Count Molecule
Proteins (2 molecules)
2
Lipopolysaccharide Export System Protein Lptc
Molecule annotation
Chemical (1 molecule)
1
1
* Click molecule labels to explore molecular sequence information.

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