Characterization of the gene cassette required for biosynthesis of the (alpha1-->6)-linked N-acetyl-D-mannosamine-1-phosphate capsule of serogroup A Neisseria meningitidis

J Bacteriol. 1998 Mar;180(6):1533-9. doi: 10.1128/JB.180.6.1533-1539.1998.


The (alpha1-->6)-linked N-acetyl-D-mannosamine-1-phosphate meningococcal capsule of serogroup A Neisseria meningitidis is biochemically distinct from the sialic acid-containing capsules produced by other disease-associated meningococcal serogroups (e.g., B, C, Y, and W-135). We defined the genetic cassette responsible for expression of the serogroup A capsule. The cassette comprised a 4,701-bp nucleotide sequence located between the outer membrane capsule transporter gene, ctrA, and galE, encoding the UDP-glucose-4-epimerase. Four open reading frames (ORFs) not found in the genomes of the other meningococcal serogroups were identified. The first serogroup A ORF was separated from ctrA by a 218-bp intergenic region. Reverse transcriptase (RT) PCR and primer extension studies of serogroup A mRNA showed that all four ORFs were cotranscribed in the opposite orientation to ctrA and that transcription of the ORFs was initiated from the intergenic region by a sigma-70-type promoter that overlapped the ctrA promoter. The first ORF exhibited 58% amino acid identity with the UDP-N-acetyl-D-glucosamine (UDP-GlcNAc) 2-epimerase of Escherichia coli, which is responsible for the conversion of UDP-GlcNAc into UDP-N-acetyl-D-mannosamine. Polar or nonpolar mutagenesis of each of the ORFs resulted in an abrogation of serogroup A capsule production as determined by colony immunoblots and enzyme-linked immunosorbent assay. Replacement of the serogroup A biosynthetic gene cassette with a serogroup B cassette by transformation resulted in capsule switching from a serogroup A capsule to a serogroup B capsule. These data indicate that assembly of the serogroup A capsule likely begins with monomeric UDP-GlcNAc and requires proteins encoded by three other genes found in the serogroup A N. meningitidis-specific operon located between ctrA and galE.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Bacterial Capsules / biosynthesis
  • Bacterial Capsules / genetics
  • Bacterial Capsules / immunology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Base Sequence
  • Carbohydrate Epimerases / genetics
  • Carbohydrate Epimerases / metabolism
  • Chromosomes, Bacterial
  • Cloning, Molecular
  • DNA, Bacterial / analysis
  • DNA, Bacterial / genetics
  • DNA-Binding Proteins*
  • Escherichia coli Proteins*
  • Genes, Bacterial
  • Hexosamines / biosynthesis*
  • Hexosamines / genetics*
  • Hexosamines / immunology
  • Immunoblotting
  • Molecular Sequence Data
  • Mutagenesis, Insertional
  • Neisseria meningitidis / genetics*
  • Neisseria meningitidis / immunology
  • Neisseria meningitidis / metabolism*
  • Open Reading Frames
  • Operon
  • Plasmids
  • Polymerase Chain Reaction
  • Promoter Regions, Genetic
  • RNA, Messenger / analysis
  • RNA, Messenger / metabolism
  • Sequence Analysis, DNA
  • Transcription Factors*
  • Transcription, Genetic
  • Transformation, Genetic
  • UDPglucose 4-Epimerase / genetics*
  • UDPglucose 4-Epimerase / metabolism
  • Uridine Diphosphate N-Acetylglucosamine / metabolism
  • Uridine Diphosphate Sugars / metabolism


  • Bacterial Proteins
  • CtrA protein, Caulobacter
  • DNA, Bacterial
  • DNA-Binding Proteins
  • Escherichia coli Proteins
  • Hexosamines
  • RNA, Messenger
  • Transcription Factors
  • Uridine Diphosphate Sugars
  • uridine diphosphate N-acetylmannosamine
  • Uridine Diphosphate N-Acetylglucosamine
  • Carbohydrate Epimerases
  • UDP acetylglucosamine-2-epimerase
  • wecB protein, E coli
  • UDPglucose 4-Epimerase
  • galactose epimerase
  • N-acetylmannosamine

Associated data

  • GENBANK/AF019760