8F7N

Crystal structure of chemoreceptor McpZ ligand sensing domain

Summary for 8F7N

• Entry DOI: 10.2210/pdb8f7n/pdb
• Descriptor: Methyl-accepting chemotaxis protein, YTTERBIUM (III) ION (3 entities in total)
• Functional Keywords: mcp (methyl-accepting chemotaxis protein), chemotaxis, chemoreceptor, signaling protein
• Biological source: Sinorhizobium meliloti
• Total number of polymer chains: 1
• Total formula weight: 43532.56

Authors

Salar, S.,Schubot, F.D. (deposition date: 2022-11-19, release date: 2023-07-05, Last modification date: 2023-10-04)

Primary citation

Salar, S.,Ball, N.E.,Baaziz, H.,Nix, J.C.,Sobe, R.C.,Compton, K.K.,Zhulin, I.B.,Brown, A.M.,Scharf, B.E.,Schubot, F.D.
The structural analysis of the periplasmic domain of Sinorhizobium meliloti chemoreceptor McpZ reveals a novel fold and suggests a complex mechanism of transmembrane signaling.
Proteins, 91:1394-1406, 2023

PubMed Abstract: Chemotaxis is a fundamental process whereby bacteria seek out nutrient sources and avoid harmful chemicals. For the symbiotic soil bacterium Sinorhizobium meliloti, the chemotaxis system also plays an essential role in the interaction with its legume host. The chemotactic signaling cascade is initiated through interactions of an attractant or repellent compound with chemoreceptors or methyl-accepting chemotaxis proteins (MCPs). S. meliloti possesses eight chemoreceptors to mediate chemotaxis. Six of these receptors are transmembrane proteins with periplasmic ligand-binding domains (LBDs). The specific functions of McpW and McpZ are still unknown. Here, we report the crystal structure of the periplasmic domain of McpZ (McpZPD) at 2.7 Å resolution. McpZPD assumes a novel fold consisting of three concatenated four-helix bundle modules. Through phylogenetic analyses, we discovered that this helical tri-modular domain fold arose within the Rhizobiaceae family and is still evolving rapidly. The structure, offering a rare view of a ligand-free dimeric MCP-LBD, reveals a novel dimerization interface. Molecular dynamics calculations suggest ligand binding will induce conformational changes that result in large horizontal helix movements within the membrane-proximal domains of the McpZPD dimer that are accompanied by a 5 Å vertical shift of the terminal helix toward the inner cell membrane. These results suggest a mechanism of transmembrane signaling for this family of MCPs that entails both piston-type and scissoring movements. The predicted movements terminate in a conformation that closely mirrors those observed in related ligand-bound MCP-LBDs.

PubMed: 37213073
DOI: 10.1002/prot.26510

Experimental method

X-RAY DIFFRACTION (2.7 Å)