Structure and signaling mechanism of Helicobacter pylori transducer-like protein D
Chemoreceptors, or methyl-accepting chemotaxis proteins (MCPs), are ancient and widespread prokaryotic sensors that direct taxis in response to stimuli and are attractive targets for therapeutic control of bacteria 1-4. Decades of study have yielded substantial mechanistic insight into chemoreceptor function, but the absence of high-resolution full-length structures containing ligand-binding domains (LBD) has limited understanding of how effector sensing is structurally coupled to long-range signal transduction. Here, we present the intact structure of the chemoreceptor transducer-like protein D (TlpD) from the gastric pathogen Helicobacter pylori, in complex with its ligand Zn2+, determined by X-ray crystallography in two crystal forms at 2.4-3.0 [A]. Three different conformations are captured, revealing how interactions in the ligand-binding site of the chemoreceptor zinc-binding (CZB) domain are interconnected with the distal kinase interface. Small changes at the ligand-binding site coincide with cascades of side-chain rearrangements across the dimer, distortion of the receptor coiled-coil, and conformational and dynamic shifts at the kinase interface over 140 [A] away. These near-atomic resolution structures provide a framework for understanding cooperativity and allosteric communication in chemoreceptors, and establish a representative model for a widespread class of soluble chemoreceptors important in bacterial pathogenesis 2,5.