Deduced products of C4-dicarboxylate transport regulatory genes ofRhizobiumleguminosarum are homologous to nitrogen regulatory gene products

Abstract

We have sequenced two genes dctB and dctD required for the activation of the C-dicarboxylate transport structural gene dctA in free-living Rhizobium leguminosarum. The hydropathic profile of the dctB gene product (DctB) suggested that its N-terminal region may be located in the periplasm and its C-terminal region of DctB was strongly consergved with similar regions of the products of several regulatory genes that may act as environmental sensors, including ntrB, envZ, virA, phoR, strongly conserved with N-terminal domain of the dctD gene product (DctD) was strongly conserved with N-terminal domains of the products of several regulatory genes thought to be transcriptional activators, including ntrC, ompR, cirG, phoB and sfrA. In addition, the central and c-terminal regions of DctD were stronglyu conserved with the products of ntrC and nifA, transcriptionsl activatiors that require the alternate sigma factor rpoN (ntrA) as co-activator. The central region of DctD also contained a potential ATP-binding domain. These results are consistent with recent results that show that rpoN product is required for dctA activation, and suggest that DctB plus DctD-mediated transcriptional activation of dctA may be mechanistically similar to NtrB plus NtrC-mkediated activation of glanA in E. coli.