9B8I
Cryo-EM structure of the E. coli cellulose synthase BcsB-BcsC fusion protein
Summary for 9B8I
| Entry DOI | 10.2210/pdb9b8i/pdb |
| EMDB information | 44346 |
| Descriptor | Cellulose synthase BcsB-BcsC fusion protein (1 entity in total) |
| Functional Keywords | bacterial cellulose synthesis, cellulose export, outer membrane porin, periplasmic protein, structural protein |
| Biological source | Escherichia coli More |
| Total number of polymer chains | 1 |
| Total formula weight | 99242.46 |
| Authors | Verma, P.,Zimmer, J. (deposition date: 2024-03-30, release date: 2025-02-19, Last modification date: 2025-02-26) |
| Primary citation | Verma, P.,Ho, R.,Chambers, S.A.,Cegelski, L.,Zimmer, J. Insights into phosphoethanolamine cellulose synthesis and secretion across the Gram-negative cell envelope. Nat Commun, 15:7798-7798, 2024 Cited by PubMed Abstract: Phosphoethanolamine (pEtN) cellulose is a naturally occurring modified cellulose produced by several Enterobacteriaceae. The minimal components of the E. coli cellulose synthase complex include the catalytically active BcsA enzyme, a hexameric semicircle of the periplasmic BcsB protein, and the outer membrane (OM)-integrated BcsC subunit containing periplasmic tetratricopeptide repeats (TPR). Additional subunits include BcsG, a membrane-anchored periplasmic pEtN transferase associated with BcsA, and BcsZ, a periplasmic cellulase of unknown biological function. While cellulose synthesis and translocation by BcsA are well described, little is known about its pEtN modification and translocation across the cell envelope. We show that the N-terminal cytosolic domain of BcsA positions three BcsG copies near the nascent cellulose polymer. Further, the semicircle's terminal BcsB subunit tethers the N-terminus of a single BcsC protein in a trans-envelope secretion system. BcsC's TPR motifs bind a putative cello-oligosaccharide near the entrance to its OM pore. Additionally, we show that only the hydrolytic activity of BcsZ but not the subunit itself is necessary for cellulose secretion, suggesting a secretion mechanism based on enzymatic removal of translocation incompetent cellulose. Lastly, protein engineering introduces cellulose pEtN modification in orthogonal cellulose biosynthetic systems. These findings advance our understanding of pEtN cellulose modification and secretion. PubMed: 39242554DOI: 10.1038/s41467-024-51838-0 PDB entries with the same primary citation |
| Experimental method | ELECTRON MICROSCOPY (3.18 Å) |
Structure validation
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