1v0e
From Proteopedia
Endosialidase of Bacteriophage K1F
Structural highlights
FunctionFIBER_BPK1F Responsible for initial absorption of the phage to the host bacterium. Degrades the alpha-2,8-linked polysialic acid K1 capsule by cleaving within the polymer chain of polysialic acid.[1] [2] The C-terminal chaperone protein mediates homotrimerization and proper folding of the catalytic endo-N trimer.[3] Publication Abstract from PubMedPhages infecting the polysialic acid (polySia)-encapsulated human pathogen Escherichia coli K1 are equipped with capsule-degrading tailspikes known as endosialidases, which are the only identified enzymes that specifically degrade polySia. As polySia also promotes cellular plasticity and tumor metastasis in vertebrates, endosialidases are widely applied in polySia-related neurosciences and cancer research. Here we report the crystal structures of endosialidase NF and its complex with oligomeric sialic acid. The structure NF, which reveals three distinct domains, indicates that the unique polySia specificity evolved from a combination of structural elements characteristic of exosialidases and bacteriophage tailspike proteins. The endosialidase assembles into a catalytic trimer stabilized by a triple beta-helix. Its active site differs markedly from that of exosialidases, indicating an endosialidase-specific substrate-binding mode and catalytic mechanism. Residues essential for endosialidase activity were identified by structure-based mutational analysis. Crystal structure of the polysialic acid-degrading endosialidase of bacteriophage K1F.,Stummeyer K, Dickmanns A, Muhlenhoff M, Gerardy-Schahn R, Ficner R Nat Struct Mol Biol. 2005 Jan;12(1):90-6. Epub 2004 Dec 19. PMID:15608653[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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