The vbs genes that direct synthesis of the siderophore vicibactin in Rhizobium leguminosarum: their expression in other genera requires ECF sigma factor Rpol
UNSPECIFIED. (2002) The vbs genes that direct synthesis of the siderophore vicibactin in Rhizobium leguminosarum: their expression in other genera requires ECF sigma factor Rpol. MOLECULAR MICROBIOLOGY, 44 (5). pp. 1153-1166. ISSN 0950-382XFull text not available from this repository.
A cluster of eight genes, vbsGSO , vbsADL , vbsC and vbsP , are involved in the synthesis of vicibactin, a cyclic, trihydroxamate siderophore made by the symbiotic bacterium Rhizobium leguminosarum . None of these vbs genes was required for symbiotic N-2 fixation on peas or Vicia . Transcription of vbsC , vbsGSO and vbsADL (but not vbsP ) was enhanced by growth in low levels of Fe. Transcription of vbsGSO and vbsADL , but not vbsP or vbsC , required the closely linked gene rpoI , which encodes an ECF sigma factor of RNA polymerase. Transfer of the cloned vbs genes, plus rpoI , to Rhodobacter , Paracoccus and Sinorhizobium conferred the ability to make vicibactin on these other genera. We present a biochemical genetic model of vicibactin synthesis, which accommodates the phenotypes of different vbs mutants and the homologies of the vbs gene products. In this model, VbsS, which is similar to many non-ribosomal peptide synthetase multienzymes, has a central role. It is proposed that VbsS activates L-N (5) -hydroxyornithine via covalent attachment as an acyl thioester to a peptidyl carrier protein domain. Subsequent VbsA-catalysed acylation of the hydroxyornithine, followed by VbsL-mediated epimerization and acetylation catalysed by VbsC, yields the vicibactin subunit, which is then trimerized and cyclized by the thioesterase domain of VbsS to give the completed siderophore.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry
Q Science > QR Microbiology
|Journal or Publication Title:||MOLECULAR MICROBIOLOGY|
|Publisher:||BLACKWELL PUBLISHING LTD|
|Number of Pages:||14|
|Page Range:||pp. 1153-1166|
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