Part:BBa_K5246015

HB HfsC Polysaccharide polymerase

Usage and Biology

Gene HfsC from Hirschia baltica, encoding a protein of 454 amino acids polymerases repeats of monomers into a mature holdfast polymer. Deletion of polysaccharide polymerase gene hfsC in C.Crescentus didn't cause holdfast synthesis defects because of its paralogue - HfsI. Double mutants of HfsC and HfsI cause severe holdfast synthesis defects

Sequence and Features

Assembly Compatibility:

• 10
  COMPATIBLE WITH RFC[10]
• 12
  COMPATIBLE WITH RFC[12]
• 21
  COMPATIBLE WITH RFC[21]
• 23
  COMPATIBLE WITH RFC[23]
• 25
  INCOMPATIBLE WITH RFC[25]

  Illegal AgeI site found at 889
  
• 1000
  COMPATIBLE WITH RFC[1000]

Experimental characterization

Bioinformatic analysis

CDD analysis showed that only part of the protein resembles established conservative domains. The predicted domain is part of the O-antigen ligase family, which is a group of proteins responsible for outer membrane lipopolysaccharide synthesis in E. coli.

Protein BLAST also showed partial similarities with E.Coli O-antigen ligases suggested by the CDD analysis.

DeepTMHMM predicted that the protein is embedded in the membrane, crossing it approximately 12 times. This prediction is supported by structural evidence from AlphaFold 3, which shows 12 helices. A pTM score above 0.5 suggests that the predicted overall structure may closely resemble the true protein fold, while ipTM indicates the accuracy of the subunit positioning within the complex. Values higher than 0.8 represent confident, high-quality predictions.

Considering the data, HfsC is most probably a membrane protein that functions as a polysaccharide ligase due to its similarity to O-antigen ligase; this hypothesis is further supported by earlier research. [1][2]

References

1. Smith, C.S. et al. (2003a) ‘Identification of genes required for synthesis of the adhesive holdfast in Caulobacter crescentus’, Journal of Bacteriology, 185(4), pp. 1432–1442. doi:10.1128/jb.185.4.1432-1442.2003.
2. Toh, E., Kurtz, Harry D. and Brun, Y.V. (2008) ‘Characterization of the Caulobacter crescentus holdfast polysaccharide biosynthesis pathway reveals significant redundancy in the initiating glycosyltransferase and polymerase steps’, Journal of Bacteriology, 190(21), pp. 7219–7231. doi:10.1128/jb.01003-08.