J Biol Chem
From the Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115,
Published: April 2018
Many pathogenic bacteria, including , possess a pathway for the cellular export of a single serine-rich-repeat protein that mediates the adhesion of bacteria to host cells and the extracellular matrix. This adhesin protein is -glycosylated by several cytosolic glycosyltransferases and requires three accessory Sec proteins (Asp1-3) for export, but how the adhesin protein is processed for export is not well understood. Here, we report that the adhesin GspB is sequentially -glycosylated by three enzymes (GtfA/B, Nss, and Gly) that attach -acetylglucosamine and glucose to Ser/Thr residues. We also found that modified GspB is transferred from the last glycosyltransferase to the Asp1/2/3 complex. Crystal structures revealed that both Asp1 and Asp3 are related to carbohydrate-binding proteins, suggesting that they interact with carbohydrates and bind glycosylated adhesin, a notion that was supported by further analyses. We further observed that Asp1 also has an affinity for phospholipids, which is attenuated by Asp2. In summary, our findings support a model in which the GspB adhesin is sequentially glycosylated by GtfA/B, Nss, and Gly and then transferred to the Asp1/2/3 complex in which Asp1 mediates the interaction of the Asp1/2/3 complex with the lipid bilayer for targeting of matured GspB to the export machinery.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5892584 | PMC |
http://dx.doi.org/10.1074/jbc.RA117.000963 | DOI Listing |
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