UniProt functional annotation for Q858B1

UniProt codes: Q04830, Q858B1.

Organism: Enterobacteria phage K1F (Bacteriophage K1F).
Taxonomy: Viruses; dsDNA viruses, no RNA stage; Caudovirales; Podoviridae; Autographivirinae; T7virus.
 
Function: Tail spike protein: 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. {ECO:0000269|PubMed:20096705, ECO:0000269|PubMed:3546309}.
 
Function: C-terminal chaperone protein: The C-terminal chaperone protein mediates homotrimerization and proper folding of the catalytic endo-N trimer. {ECO:0000269|PubMed:12556457}.
 
Catalytic activity: Endohydrolysis of (2->8)-alpha-sialosyl linkages in oligo- or poly(sialic) acids. {ECO:0000269|PubMed:12556457, ECO:0000269|PubMed:19189967, ECO:0000269|PubMed:3546309}.
Biophysicochemical properties: Kinetic parameters: KM=71 uM for poly-alpha-2,8-sialosyl carbohydrates {ECO:0000269|PubMed:3546309}; KM=1.2 mM for oligo-alpha-2,8-sialosyl carbohydrates {ECO:0000269|PubMed:3546309}; KM=7.1 uM for poly-alpha-2,8-alpha-2,9-sialosyl carbohydrates {ECO:0000269|PubMed:3546309}; Vmax=19 umol/min/mg enzyme for poly-alpha-2,8-sialosyl carbohydrates cleavage {ECO:0000269|PubMed:3546309}; Vmax=18 umol/min/mg enzyme for oligo-alpha-2,8-sialosyl carbohydrates cleavage {ECO:0000269|PubMed:3546309}; Vmax=13 umol/min/mg enzyme for poly-alpha-2,8-alpha-2,9-sialosyl carbohydrates {ECO:0000269|PubMed:3546309};
Subunit: Tail spike protein: Homotrimer (PubMed:3546309, PubMed:20124697). Interacts with sialic acid (PubMed:15608653, PubMed:20096705). {ECO:0000269|PubMed:15608653, ECO:0000269|PubMed:20096705, ECO:0000269|PubMed:20124697, ECO:0000269|PubMed:3546309}.
Subcellular location: Tail spike protein: Virion. Note=Tail spike. {ECO:0000269|PubMed:8331067}.
Ptm: Proteolytic cleavage and release of the chaperone stabilizes the folded protein. {ECO:0000269|PubMed:12556457, ECO:0000269|PubMed:19189967}.
Similarity: Belongs to the glycosyl hydrolase 58 family. {ECO:0000305}.
Sequence caution: Sequence=AAC37340.1; Type=Frameshift; Positions=914; Evidence={ECO:0000305};

Annotations taken from UniProtKB at the EBI.