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CB2/CB2A HfsE Integral membrane glycosyltransferases

Introduction

Usage and Biology

Encodes a protein of 512 amino acids, integral membrane glycosyltransferases from the polyisoprenylphosphate hexose-1-phosphate transferase (PHPT) family , transferrs hexose-1-phosphate residues from UDP-hexoses to the lipid carrier molecule undecaprenol phosphate in the inner membrane. In C.Crescentus catalyzes the first step in polysaccharide biosynthesis by transferring glucose-1-phosphate residues from UDP-glucoses to the lipid carrier molecule undecaprenol phosphate in the inner membrane Studies using hfsE mutants showed minimal changes in holdfast synthesis and bacterial adhesion. Through further genome analysis two paralogs, pssY and pssZ, were identified as potential substitutes for the hfsE protein in holdfast synthesis. However, double combination mutants did not have a substantial decrease of neither surface adherence nor inability to synthesize holdfast, but had a slight misplacement at the tip of the stalk. While hfsE, pssY and pssZ triple deletion mutant, was unable to produce holdfast or adhere to surfaces. [2]"

Sequence and Features

Experimental characterization

Bioinformatic analysis

According to CDD, protein is similar to undecaprenyl-phosphate glucose phosphotransferases found in E. coli. Most of the genes for these proteins are found within large operons dedicated to the production of complex exopolysaccharides such as the enterobacterial O-antigen. It also has some overlap with other bacterial sugar-transferases.

Protein BLAST further supports the prediction of HfsE being a UDP-glucose-carrier transferase because of its similarities with multiple glucose transferases.

HfsE is likely a transmembrane protein that traverses the membrane six times, with a portion of it exposed on the cytoplasmic side.

AlphaFold 3 structure confidence scores suggest that it is a protein made mostly of alpha 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 prediction (Fig.1).

Altogether, HfsE is a membrane protein that is responsible for the first glucose addition to an undecaprenyl-phosphate lipid carrier in the holdfast synthesis pathway, similar to bacterial glucose transferases. Analogous HfsE function is proposed in the literature by earlier research. [1][2][3]

References

1. Patel, K.B. et al. (2012) ‘Functional characterization of UDP-glucose:undecaprenyl-phosphate glucose-1-phosphate transferases of Escherichia coli and Caulobacter crescentus’, Journal of Bacteriology, 194(10), pp. 2646–2657. doi:10.1128/jb.06052-11.
2. Chepkwony, N.K., Berne, C. and Brun, Y.V. (2019b) ‘Comparative analysis of ionic strength tolerance between freshwater and marine Caulobacterales adhesins’, Journal of Bacteriology, 201(18). doi:10.1128/jb.00061-19.
3. Hershey, D.M., Fiebig, A. and Crosson, S. (2019a) ‘A genome-wide analysis of adhesion in Caulobacter crescentus identifies new regulatory and biosynthetic components for holdfast assembly’, mBio, 10(1). doi:10.1128/mbio.02273-18.