The opgGIH and opgC genes of Rhodobacter sphaeroides form an operon that controls backbone synthesis and succinylation of osmoregulated periplasmic glucans.
Osmoregulated periplasmic glucans (OPGs) of Rhodobacter sphaeroides are anionic cyclic molecules that accumulate in large amounts in the periplasmic space in response to low osmolarity of the medium. Their anionic character is provided by the substitution of the glucosidic backbone by succinyl residues. A wild-type strain was subject to transposon mutagenesis, and putative mutant clones were screened for changes in OPGs by thin layer chromatography. One mutant deficient in succinyl substitution of the OPGs was obtained and the gene inactivated in this mutant was characterized and named opgC. opgC is located downstream of three ORFs, opgGIH, two of which are similar to the Escherichia coli operon, mdoGH, governing OPG backbone synthesis. Inactivation of opgG, opgI or opgH abolished OPG production and complementation analysis indicated that the three genes are necessary for backbone synthesis. In contrast, inactivation of a gene similar to ndvB, encoding the OPG-glucosyl transferase in Sinorhizobium meliloti, had no consequence on OPG synthesis in Rhodobacter sphaeroides. Cassette insertions in opgH had a polar effect on glucan substitution, indicating that opgC is in the same transcription unit. Expression of opgIHC in E. coli mdoB/mdoC and mdoH mutants allowed the production of slightly anionic and abnormally long linear glucans.
Cogez
Virginie
V
Unité de Glycobiologie Structurale et Fonctionnelle, CNRS UMR8576, Université des Sciences et Technologies de Lille, France.
Gak
Evgueni
E
Puskas
Agnes
A
Kaplan
Samuel
S
Bohin
Jean-Pierre
JP
D001426:Bacterial Proteins / Q000235:genetics; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D004268:DNA-Binding Proteins; D004926:Escherichia coli / Q000235:genetics; D005936:Glucans / Q000235:genetics*; D008565:Membrane Proteins; D009154:Mutation; D009876:Operon; D010641:Phenotype; D012242:Rhodobacter sphaeroides / Q000235:genetics*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013386:Succinates / Q000378:metabolism; D037521:Virulence Factors; D014867:Water / Q000378:metabolism
C090801:AcvB protein, Agrobacterium tumefaciens; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D005936:Glucans; D008565:Membrane Proteins; C089201:NdvB protein, Rhizobium meliloti; D013386:Succinates; D037521:Virulence Factors; D014867:Water