Comparison of lipopolysaccharide biosynthesis genes rfaK, rfaL, rfaY, and rfaZ of Escherichia coli K-12 and Salmonella typhimurium

Abstract

Analysis of the sequence of a 4.3-kb region downstream of rfaJ revealed four genes. The first two of these, which encode proteins of 27,441 and 32,890 Da, were identified as rfaY and rfaZ by homology of the derived protein sequences of their products to the products of similar genes ofSalmonella typhimurium. The amino acid sequences of proteins RfaY and RfaZ showed, respectively, 70 and 72% identity. Genes 3 and 4 were identified as rfaK and rfaL on the basis of size and position, but the derived amino acid sequences of the products of these genes showed very little similarity (about 12% identity) between Escherichia coli K-12 and S. typhimurium. The next gene in the cluster, rfaC, encodes a product which also shows strong protein sequence homology between E. coli K-12 and S. typhimurium, as do the rfaF and rfaD genes which lie beyond it. Thus, the rfa gene cluster appears to consist of two blocks of genes which are conserved flanking a central region of two genes which are not conserved between these species. Although the RfaL protein sequence is not conserved, hydropathy plots of the two RfaL species are nearly identical and indicate that this is a typical integral membrane protein with 10 or more potential transmembrane domains. We noted the similarity of the structure of the ria gene cluster to that of the rfl, gene cluster, which has now been sequenced in several Salmonela serovars. The rjb cluster also contains a gene which lies within a central nonconserved region and encodes an integral membrane protein similar to protein RfaL. We speculate that protein RfaL may interact in a strain-or species-specific way with one or more Rfb proteins in the expression of surface 0 antigen.

Effect of mutations in Shigella flexneri chromosomal and plasmid‐encoded lipopolysaccharide genes on invasion and serum resistance

“…Whether the defective core or the reduction in the amount of O-antigen of the rfaX mutant affected the polar localization of IcsA remains to be determined. Although the rfaX gene has homology to E. coli rfaY (Klena et al, 1992b), it is not possible to compare the effects of rfaY mutations in different organisms, because defined rfaY mutants in E. coli or S. typhimurium have not been reported and the role of rfaY in LPS core synthesis was speculative (Schnaitman and Klena, 1993). An uncharacterized mutant of S. flexneri generated in a previous study, S2687, showed a defective LPS core having normally attached O-antigen chains (Okada et al, 1991b).…”

“…In the E. coli and S. typhimurium rfa loci, rfaZ and rfaK are located downstream of rfaY (MacLachlan et al, 1991;Klena et al, 1992b). rfaK is thought to be a GlcNAc transferase gene that is required for LPS core synthesis, and mutations in this gene reduced the size of LPS cores and almost abolished O-antigen attachment (Mä kelä and Stocker, 1984;MacLachlan et al, 1991;Klena et al, 1992a).…”

“…1A) (Schnaitman and Klena, 1993). One insert was in an ORF with homology to the 5Ј portion of E. coli rfaY, whose exact function has not been identified, but it was speculated that the gene encodes a protein involved in LPS core synthesis (Klena et al, 1992b;Schnaitman and Klena, 1993). This S. flexneri gene was named rfaX, since LPS studies (shown below) indicated that the LPS core synthesis of this mutant was affected; it is not known whether the function of this gene is equivalent to that of rfaY.…”

A novel strategy to isolate cell-envelope mutants resistant to phage infection: bacteriophage mEp213 requires lipopolysaccharides in addition to FhuA to enter Escherichia coli K-12

“…waaF encodes ADP-heptose : LPS heptosyltransferase II (Gronow, et al, 2000). The product of the waaL gene, Oantigen ligase, connects the inner core to the O antigen of LPS (Klena et al, 1992). mEp213 phage adsorption in the above three mutants showed a decrease of 25-35 % at 5 min and a decrease of~15 % at 10-15 min when compared with the adsorption using the wild-type strain W3110 (Fig.…”

Structural and genetic characterization of the Shigella boydii type 18 O antigen

“…There are several components of the gene cluster that appear to be the result of gene substitutions. In addition to the genes expected for synthesis of the S. boydii type 13 O antigen men- (24). However, there has clearly been deletion in orf10, and this gene is no longer functional.…”