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Moure, VR, Danyal, K, Yang, ZY, Wendroth, S, Müller-Santos, M, Pedrosa, FO, Scarduelli, M, Gerhardt, EC, Huergo, LF, Souza, EM and Seefeldt, LC (2013) The nitrogenase regulatory enzyme dinitrogenase reductase ADP-ribosyltransferase (DraT) is activated by direct interaction with the signal transduction protein GlnB. J. Bacteriol. 195:279-86


Fe protein (dinitrogenase reductase) activity is reversibly inactivated by dinitrogenase reductase ADP-ribosyltransferase (DraT) in response to an increase in the ammonium concentration or a decrease in cellular energy in Azospirillum brasilense, Rhodospirillum rubrum, and Rhodobacter capsulatus. The ADP-ribosyl is removed by the dinitrogenase reductase-activating glycohydrolase (DraG), promoting Fe protein reactivation. The signaling pathway leading to DraT activation by ammonium is still not completely understood, but the available evidence shows the involvement of direct interaction between the enzyme and the nitrogen-signaling P(II) proteins. In A. brasilense, two P(II) proteins, GlnB and GlnZ, were identified. We used Fe protein from Azotobacter vinelandii as the substrate to assess the activity of A. brasilense DraT in vitro complexed or not with P(II) proteins. Under our conditions, GlnB was necessary for DraT activity in the presence of Mg-ADP. The P(II) effector 2-oxoglutarate, in the presence of Mg-ATP, inhibited DraT-GlnB activity, possibly by inducing complex dissociation. DraT was also activated by GlnZ and by both uridylylated P(II) proteins, but not by a GlnB variant carrying a partial deletion of the T loop. Kinetics studies revealed that the A. brasilense DraT-GlnB complex was at least 18-fold more efficient than DraT purified from R. rubrum, but with a similar K(m) value for NAD(+). Our results showed that ADP-ribosylation of the Fe protein does not affect the electronic state of its metal cluster and prevents association between the Fe and MoFe proteins, thus inhibiting electron transfer.


PubMed PMC3553828 Online version:10.1128/JB.01517-12


ADP Ribose Transferases/isolation & purification; ADP Ribose Transferases/metabolism; Adenosine Diphosphate/metabolism; Azospirillum brasilense/enzymology; Azotobacter vinelandii/enzymology; Bacterial Proteins/metabolism; Coenzymes; Enzyme Inhibitors/metabolism; Ketoglutaric Acids/metabolism; Kinetics; Magnesium/metabolism; NAD/metabolism; Oxidoreductases/isolation & purification; Oxidoreductases/metabolism; PII Nitrogen Regulatory Proteins/metabolism; Protein Binding



Gene product Qualifier GO Term Evidence Code with/from Aspect Extension Notes Status


GO:0006471: protein ADP-ribosylation



Figure 2 shows activation and interaction with different PII proteins that form in vitro complexes and the Fe protein. Fe protein activity, and thus, DraT activity was measured by the evolution of hydrogen.

CACAO 9022


GO:0006808: regulation of nitrogen utilization



Figure 1. Preincubation of the Fe protein with DraT in the presence of increasing concentrations of GlnB resulted in Fe protein inhibition in a GlnB-dependent manner

CACAO 9168

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