2lpm

Publication Abstract from PubMed

Receiver domains control intracellular responses triggered by signal transduction in bacterial two-component systems. Here, we report the solution nuclear magnetic resonance structure and dynamics of Sma0114 from the bacterium Sinorhizobium meliloti, the first such characterization of a receiver domain from the HWE-kinase family of two-component systems. The structure of Sma0114 adopts a prototypical alpha(5)/beta(5) Rossman fold but has features that set it apart from other receiver domains. The fourth beta-strand of Sma0114 houses a PFxFATGY sequence motif, common to many HWE-kinase-associated receiver domains. This sequence motif in Sma0114 may substitute for the conserved Y-T coupling mechanism, which propagates conformational transitions in the 455 (alpha4-beta5-alpha5) faces of receiver domains, to prime them for binding downstream effectors once they become activated by phosphorylation. In addition, the fourth alpha-helix of the consensus 455 face in Sma0114 is replaced with a segment that shows high flexibility on the pico- to nanosecond time scale by (15)N relaxation data. Secondary structure prediction analysis suggests that the absence of helix alpha4 may be a conserved property of the HWE-kinase-associated family of receiver domains to which Sma0114 belongs. In spite of these differences, Sma0114 has a conserved active site, binds divalent metal ions such as Mg(2+) and Ca(2+) that are required for phosphorylation, and exhibits micro- to millisecond active-site dynamics similar to those of other receiver domains. Taken together, our results suggest that Sma0114 has a conserved active site but differs from typical receiver domains in the structure of the 455 face that is used to effect signal transduction following activation.

Nuclear Magnetic Resonance Structure and Dynamics of the Response Regulator Sma0114 from Sinorhizobium meliloti.,Sheftic SR, Garcia PP, White E, Robinson VL, Gage DJ, Alexandrescu AT Biochemistry. 2012 Sep 4;51(35):6932-41. Epub 2012 Aug 21. PMID:22880754^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.