Rhodobacter capsulatus AnfA is essential for production of Fe-nitrogenase proteins but dispensable for cofactor biosynthesis and electron supply.

The photosynthetic α-proteobacterium Rhodobacter capsulatus reduces and thereby fixes atmospheric dinitrogen (N ) by a molybdenum (Mo)-nitrogenase and an iron-only (Fe)-nitrogenase. Differential expression of the structural genes of Mo-nitrogenase (nifHDK) and Fe-nitrogenase (anfHDGK) is strictly controlled and activated by NifA and AnfA, respectively. In contrast to NifA-binding sites, AnfA-binding sites are poorly defined.

NifA is the master regulator of both nitrogenase systems in Rhodobacter capsulatus.

Rhodobacter capsulatus fixes atmospheric nitrogen (N ) by a molybdenum (Mo)-nitrogenase and a Mo-free iron (Fe)-nitrogenase, whose production is induced or repressed by Mo, respectively. At low nanomolar Mo concentrations, both isoenzymes are synthesized and contribute to nitrogen fixation. Here we examined the regulatory interplay of the central transcriptional activators NifA and AnfA by proteome profiling.

Coordinated regulation of nitrogen fixation and molybdate transport by molybdenum.

Biological nitrogen fixation, the reduction of chemically inert dinitrogen to bioavailable ammonia, is a central process in the global nitrogen cycle highly relevant for life on earth. N reduction to NH is catalyzed by nitrogenases exclusively synthesized by diazotrophic prokaryotes. All diazotrophs have a molybdenum nitrogenase containing the unique iron-molybdenum cofactor FeMoco.

Bacterial PerO Permeases Transport Sulfate and Related Oxyanions.

synthesizes the high-affinity ABC transporters CysTWA and ModABC to specifically import the chemically related oxyanions sulfate and molybdate, respectively. In addition, has the low-affinity permease PerO acting as a general oxyanion transporter, whose elimination increases tolerance to molybdate and tungstate. Although PerO-like permeases are widespread in bacteria, their function has not been examined in any other species to date.

Molybdate uptake by Agrobacterium tumefaciens correlates with the cellular molybdenum cofactor status.

Many enzymes require the molybdenum cofactor, Moco. Under Mo-limiting conditions, the high-affinity ABC transporter ModABC permits molybdate uptake and Moco biosynthesis in bacteria. Under Mo-replete conditions, Escherichia coli represses modABC transcription by the one-component regulator, ModE, consisting of a DNA-binding and a molybdate-sensing domain.