Fig. 4.
CPS gene loci in Gram-negative bacteria expressing ABC-transporter dependent CPS assembly pathways. (a) Gene loci encoding enzymes and transport proteins required for assembly of Group 2 E. coli K-antigens K1 (polysialic acid), K4 (chondroitin), and K5 (heparosan). Genes encoded by Regions 1 and 3 are well-conserved within Group 2 E. coli strains and encode enzymes required for CPS translocation across the cell wall, while Region 2 encodes CPS-specific glycosyltransferases and other biosynthetic enzymes. (b) Gene locus encoding proteins required for assembly of N. meningitidis serogroup B CPS. Region A encodes CPS-specific biosynthetic enzymes and varies between serogroups, while Regions B-E are highly conserved in all N. meningitidis serogroups. Regions B and C encode CPS translocation proteins homologous to genes in Regions 1 and 3 of Group 2 E. coli (homologous genes connected with gray bands), Regions D and D′ encode LPS assembly genes, and Region E has no known function. (c) Gene loci encoding P. multocida type A, D, and F CPS biosynthetic and transport proteins. Region 1 and 3 encode translocation genes whose functions are relatively well conserved in P. multocida, and Region 2 encodes CPS biosynthetic enzymes unique to the serotype specified. Homologous inter-species transport genes are color-coded and connected by bands of matching colors. Genes encoding glycosyltransferases are illustrated as white arrows with black outline and glycosyltransferase activity denoted within (bifunctional glycosyltransferases are labeled as found in nature, with N-terminal domain displayed at 5′ end of gene and C-terminal domain displayed at 3′ end of gene). UDP-glucose dehydrogenase is frequently encoded in CPS-specific biosynthetic clusters and is indicated here with diagonal lines. Other genes with known and putative homologs are designated with matching numbers. Note: genes and operons are not drawn to scale.