title: The rkp-3 gene region of Sinorhizobium meliloti Rm41 contains strain-specific genes that determine K antigen structure.
abstract: The rkp-3 region is indispensable for capsular polysaccharide (K antigen) synthesis in Sinorhizobium meliloti Rm41. Strain Rm41 produces a K antigen of strain-specific structure, designated as the KR5 antigen. The data in this report show that the rkp-3 gene region comprises 10 open reading frames involved in bacterial polysaccharide synthesis and export. The predicted amino acid sequences for the rkpL-Q gene products are homologous to enzymes involved in the production of specific sugar moieties, while the putative products of the rkpRST genes show a high degree of similarity to proteins required for transporting polysaccharides to the cell surface. Southern analysis experiments using gene-specific probes suggest that genes involved in the synthesis of the precursor sugars are unique in strain Rm41, whereas sequences coding for export proteins are widely distributed among Sinorhizobium species. Mutations in the rkpL-Q genes result in a modified K antigen pattern and impaired symbiotic capabilities. On this basis, we suggest that these genes are required for the production of the KR5 antigen that is necessary for S. meliloti Rm41 exoB (AK631)-alfalfa (Medicago sativa) symbiosis.
authors.affiliation: Institute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged.
authors.forename: E
authors.initials: E
authors.lastname: Kiss
authors.forename: A
authors.initials: A
authors.lastname: Kereszt
authors.forename: F
authors.initials: F
authors.lastname: Barta
authors.forename: S
authors.initials: S
authors.lastname: Stephens
authors.forename: B L
authors.initials: BL
authors.lastname: Reuhs
authors.forename: A
authors.initials: A
authors.lastname: Kondorosi
authors.forename: P
authors.initials: P
authors.lastname: Putnoky
mesh_terms: D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics; D000954:Antigens, Surface / Q000737:chemistry / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D015183:Restriction Mapping; D020539:Sequence Analysis, Protein; D016962:Sinorhizobium meliloti / Q000145:classification / Q000201:enzymology / Q000235:genetics*; D013045:Species Specificity
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001426:Bacterial Proteins; C030659:K antigens