NMR Structure of the HWE Kinase Associated Response Regulator Sma0114 in Its Activated State

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• 作者：Sarah R. Sheftic ; Emma White ; Daniel J. Gage ; Andrei T. Alexandrescu
• 刊名：Biochemistry
• 出版年：2014
• 出版时间：January 21, 2014
• 年：2014
• 卷：53
• 期：2
• 页码：311-322
• 全文大小：656K
• ISSN：1520-4995

文摘

Bacterial receiver domains modulate intracellular responses to external stimuli in two-component systems. Sma0114 is the first structurally characterized representative from the family of receiver domains that are substrates for histidine-tryptophan-glutamate (HWE) kinases. We report the NMR structure of Sma0114 bound by Ca²⁺ and BeF₃^{鈥?/sup>, a phosphate analogue that stabilizes the activated state. Differences between the NMR structures of the inactive and activated states occur in helix 伪1, the active site loop that connects strand 尾3 and helix 伪3, and in the segment from strand 尾5 to helix 伪5 of the 455 (伪4-尾5-伪5) face. Structural rearrangements of the 455 face typically make receiver domains competent for binding downstream target molecules. In Sma0114 the structural changes accompanying activation result in a more negatively charged surface for the 455 face. Coupling between the 455 face and active site phosphorylation is usually mediated through the rearrangement of a threonine and tyrosine residue, in a mechanism called Y鈥揟 coupling. The NMR structure indicates that Sma0114 lacks Y鈥揟 coupling and that communication between the active site and the 455 face is achieved through a conserved lysine residue that stabilizes the acyl phosphate in receiver domains. 15N-NMR relaxation experiments were used to investigate the backbone dynamics of the Sma0114 apoprotein, the binary Sma0114路Ca2+ complex, and the ternary Sma0114路Ca2+路BeF₃鈥?/sup> complex. The loss of entropy due to ligand binding at the active site is compensated by increased flexibility in the 455 face. The dynamic character of the 455 face in Sma0114, which results in part from the replacement of helix 伪4 by a flexible loop, may facilitate induced-fit recognition of target molecules.}