Structural characterization of closely related O-antigen lipopolysaccharide (LPS) chain length regulators |
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Authors: | Kalynych Sergei Yao Deqiang Magee James Cygler Miroslaw |
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Affiliation: | Department of Biochemistry, McGill University, Montreal, Quebec H3G 0B1, Canada. |
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Abstract: | The surface O-antigen polymers of Gram-negative bacteria exhibit a modal length distribution that depends on dedicated chain length regulator periplasmic proteins (polysaccharide co-polymerases, PCPs) anchored in the inner membrane by two transmembrane helices. In an attempt to determine whether structural changes underlie the O-antigen modal length specification, we have determined the crystal structures of several closely related PCPs, namely two chimeric PCP-1 family members solved at 1.6 and 2.8 Å and a wild-type PCP-1 from Shigella flexneri solved at 2.8 Å. The chimeric proteins form circular octamers, whereas the wild-type WzzB from S. flexneri was found to be an open trimer. We also present the structure of a WzzFepE mutant, which exhibits severe attenuation in its ability to produce very long O-antigen polymers. Our findings suggest that the differences in the modal length distribution depend primarily on the surface-exposed amino acids in specific regions rather than on the differences in the oligomeric state of the PCP protomers. |
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Keywords: | Cell Surface Crystal Structure Lipopolysaccharide (LPS) Mutagenesis Protein Chimeras Protein-Protein Interactions O-antigen Polysaccharide Length Control |
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