Specificity and Regulation of Interaction between the P II and AmtB 1 Proteins in Rhodospirillum rubrum

Author:

Wolfe David M.1,Zhang Yaoping1,Roberts Gary P.1

Affiliation:

1. Department of Bacteriology and the Center for the Study of Nitrogen Fixation, University of Wisconsin—Madison, Madison, Wisconsin 53706

Abstract

ABSTRACT The nitrogen regulatory protein P II and the ammonia gas channel AmtB are both found in most prokaryotes. Interaction between these two proteins has been observed in several organisms and may regulate the activities of both proteins. The regulation of their interaction is only partially understood, and we show that in Rhodospirillum rubrum one P II homolog, GlnJ, has higher affinity for an AmtB 1 -containing membrane than the other two P II homologs, GlnB and GlnK. This interaction strongly favors the nonuridylylated form of GlnJ and is disrupted by high levels of 2-ketoglutarate (2-KG) in the absence of ATP or low levels of 2-KG in the presence of ATP. ADP inhibits the destabilization of the GlnJ-AmtB 1 complex in the presence of ATP and 2-KG, supporting a role for P II as an energy sensor measuring the ratio of ATP to ADP. In the presence of saturating levels of ATP, the estimated K d of 2-KG for GlnJ bound to AmtB 1 is 340 μM, which is higher than that required for uridylylation of GlnJ in vitro, about 5 μM. This supports a model where multiple 2-KG and ATP molecules must bind a P II trimer to stimulate release of P II from AmtB 1 , in contrast to the lower 2-KG requirement for productive uridylylation of P II by GlnD.

Publisher

American Society for Microbiology

Subject

Molecular Biology,Microbiology

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