The Myxococcus xanthus rfbABC operon encodes an ATP-binding cassette transporter homolog required for O-antigen biosynthesis and multicellular development.
A wild-type sasA locus is critical for Myxococcus xanthus multicellular development. Mutations in the sasA locus cause defective fruiting body formation, reduce sporulation, and restore developmental expression of the early A-signal-dependent gene 4521 in the absence of A signal. The wild-type sasA locus has been located on a 14-kb cloned fragment of the M. xanthus chromosome. The nucleotide sequence of a 7-kb region containing the complete sasA locus was determined. Three open reading frames encoded by the genes, designated rfbA, B and C were identified. The deduced amino acid sequences of rfbA and rfbB show identity to the integral membrane domains and ATPase domains, respectively, of the ATP-binding cassette (ABC) transporter family. The highest identities are to a set of predicted ABC transporters required for the biosynthesis of lipopolysaccharide O-antigen in certain gram-negative bacteria. The rfbC gene encodes a predicted protein of 1,276 amino acids. This predicted protein contains a region of 358 amino acids that is 33.8% identical to the Yersinia enterocolitica O3 rfbH gene product, which is also required for O-antigen biosynthesis. Immunoblot analysis revealed that the sasA1 mutant, which was found to encode a nonsense codon in the beginning of rfbA, produced less O-antigen than sasA+ strains. These data indicate that the sasA locus is required for the biosynthesis of O-antigen and, when mutated, results in A-signal-independent expression of 4521.
Guo
D
D
Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston 77030, USA.
Bowden
M G
MG
Pershad
R
R
Kaplan
H B
HB
D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000483:Alleles; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D005798:Genes, Bacterial; D006836:Hydro-Lyases / Q000235:genetics; D008359:Mannose-6-Phosphate Isomerase / Q000235:genetics; D008969:Molecular Sequence Data; D009024:Morphogenesis; D009154:Mutation; D016941:Myxococcus xanthus / Q000235:genetics* / Q000254:growth & development / Q000276:immunology; D009713:Nucleotidyltransferases / Q000235:genetics; D019081:O Antigens / Q000096:biosynthesis*; D009876:Operon; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D019081:O Antigens; D009713:Nucleotidyltransferases; C085243:dTDP-D-glucose synthase; D006836:Hydro-Lyases; C022771:dTDPglucose 4,6-dehydratase; D008359:Mannose-6-Phosphate Isomerase