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In situ cryo-EM structure of bacteriophage Sf6 portal:gp7 complex at 2.7A resolution
Structural highlights
FunctionFIBER_BPSFV Non-covalently bound to the neck of the phage capsid and mediating attachment of the viral particle to host cell-surface polysaccharide. It displays endorhamnosidase enzymatic activity, hydrolyzing the alpha-1,3-O-glycosidic linkage between rhamnose and galactose of the O-antigen polysaccharide.[1] [2] [3] Publication Abstract from PubMedSf6 is a bacterial virus that infects the human pathogen Shigella flexneri. Here, we describe the cryo-electron microscopy structure of the Sf6 tail machine before DNA ejection, which we determined at a 2.7-angstrom resolution. We built de novo structures of all tail components and resolved four symmetry-mismatched interfaces. Unexpectedly, we found that the tail exists in two conformations, rotated by ~6 degrees with respect to the capsid. The two tail conformers are identical in structure but differ solely in how the portal and head-to-tail adaptor carboxyl termini bond with the capsid at the fivefold vertex, similar to a diamond held over a five-pronged ring in two nonidentical states. Thus, in the mature Sf6 tail, the portal structure does not morph locally to accommodate the symmetry mismatch but exists in two energetic minima rotated by a discrete angle. We propose that the design principles of the Sf6 tail are conserved across P22-like Podoviridae. High-resolution cryo-EM structure of the Shigella virus Sf6 genome delivery tail machine.,Li F, Hou CD, Yang R, Whitehead R 3rd, Teschke CM, Cingolani G Sci Adv. 2022 Dec 9;8(49):eadc9641. doi: 10.1126/sciadv.adc9641. Epub 2022 Dec 7. PMID:36475795[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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