gmhX, a novel gene required for the incorporation of l-glycero-d-manno-heptose into lipooligosaccharide in Neisseria meningitidis

摘要: Lipooligosaccharide (LOS) is a critical virulence factor of Neisseria meningitidis. A Tn916 insertion mutant, designated 469, was found to exhibit markedly truncated LOS 2·9 kDa when compared by Tricine/SDS-PAGE the parental (4·6 kDa). Electrospray mass spectrometry analysis 469 revealed that it consisted deep rough, heptose-deficient structure, Kdo2-lipid A. Sequencing chromosomal DNA flanking in mutant transposon had inserted into an ORF predicted encode 187 aa protein with sequence homology histidinol-phosphate phosphatase domain Escherichia coli HisB and family genes unknown function. The gene, gmhX, part polycistronic operon (ice-2) containing two other genes, nlaB orfC. encodes lysophosphatidic-acid acyltransferase orfC N-acetyltransferase. Specific polar non-polar gmhX mutations strain, NMB, exhibited structure repair mutants homologous recombination wild-type restored phenotype. GmhX demonstrated increased sensitivity polymyxin B. also killing normal human serum but were not as sensitive inner-core heptose. In genomes Helicobacter pylori Synechocystis, homologues are associated heptose biosynthesis genes; however, N. meningitidis, location distinct from gmhA, rfaD, rfaE, aut rfaC. novel enzyme required for incorporation L-glycero-D-manno-heptose meningococcal LOS, candidate 2-D-glycero-manno-heptose pathway.