A dimeric two-component receiver domain inhibits the sigma54-dependent ATPase in DctD.

Abstract

SPECIFIC AIMTwo-component signal transduction systems control a variety of behaviors such as adaptation to altered osmolarity, chemotaxis, nutrient acquisition, beneficial and harmful symbioses, and complex development pathways. Here we explore the structural basis of signal transduction in DctD, a two-component response regulator and bacterial enhancer binding protein that is essential for biological nitrogen fixation by Sinorhizobium meliloti.PRINCIPAL FINDINGSThe DctD protein has three domains: an amino-terminal regulatory domain; a central ς54-dependent ATPase domain; and a carboxyl-terminal DNA binding domain. Earlier studies showed that the carboxyl-terminal third of the DctD receiver domain exerts a negative affect on its central ATPase domain. Phosphorylation of the receiver domain overcomes this inhibition via an unknown mechanism.1. DctD (2–143) fragment is phosphorylatable and shows catalytic autodephosphorylationFunctional studies and sequence alignments define the end of the receiver domain a...