KpsC and KpsS are retaining 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo) transferases involved in synthesis of bacterial capsules

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 110; no. 51; pp. 20753 - 20758
• Main Authors: Willis, Lisa M., Whitfield, Chris
• Format: Journal Article
• Language: English
• Published: United States NATIONAL ACADEMY OF SCIENCES 17.12.2013; National Acad Sciences; National Academy of Sciences
• Subjects: ATP binding cassette transporters; Bacterial Capsules - genetics; Bacterial Capsules - metabolism; Bacterial proteins; Biological Sciences; Biosynthesis; Campylobacter jejuni; Capsules; Carrier Proteins - genetics; Carrier Proteins - metabolism; Enzymes; Escherichia coli; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Genetic Complementation Test; Genetic loci; Glucose; Gram-negative bacteria; Haemophilus influenzae; Lipids; Neisseria meningitidis; Neisseria meningitidis - genetics; Neisseria meningitidis - metabolism; O antigens; Pasteurella multocida; Polysaccharides; Proteins; Sugar Acids - metabolism; Transferases - genetics; Transferases - metabolism; Virology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1312637110

Capsular polysaccharides (CPSs) are high-molecular-mass cell-surface polysaccharides, that act as important virulence factors for many pathogenic bacteria. Several clinically important Gram-negative pathogens share similar systems for CPS biosynthesis and export; examples include Escherichia coli, Campylobacter jejuni, Haemophilus influenzae, Neisseria meningitidis, and Pasteurella multocida. Each CPS contains a serotype-specific repeat-unit structure, but the glycans all possess a lipid moiety at their reducing termini. In E. coli and N. meningitidis, the predominant lipid is a lysophosphatidylglycerol moiety that is attached to the repeat-unit domain of the CPS via multiple residues of 3-deoxy-D-manno-oct-2-ulosonic acid (Kdo), referred to as a poly-Kdo linker. The Kdo residues are β-linked, suggesting that they are synthesized by retaining glycosyltransferases. To date, the only characterized Kdo transferases are the inverting enzymes that catalyze the α-linkages found in lipopolysaccharide. Here, we identify two conserved proteins from CPS assembly systems, KpsC and KpsS, as the β-Kdo-transferases and demonstrate in vitro reconstitution of poly-Kdo linker assembly on a fluorescent phosphatidylglycerol acceptor. KpsS adds the first Kdo residue, and this reaction product is then extended by KpsC. Cross-complementation experiments demonstrate that the E. coli and N. meningitidis protein homologs are functionally conserved.