9sou

Structure of the ligand binding domain of the ancestral reconstructed Pseudomonas chemoreceptor aPcpI in complex with citrate

spinqualitylabelsall models 9sou, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 9sou is a 1 chain structure with sequence from Pseudomonas sp. SID14000. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.3Å Ligands: CIT Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Bacterial chemotaxis is essential for environmental adaptation and host interaction. To this end, bacteria have evolved exceptionally broad chemosensory capacities, with few apparent constraints on ligand structure or size. These capacities are determined by the extraordinary diversity of chemoreceptor ligand-binding domains (LBDs), which recognize chemoeffectors and evolve rapidly to acquire new functions. Many LBDs have complex architectures, often comprising multiple ligand-binding modules. Among chemoreceptor LBDs, members of the all-helical class are widespread and can contain one, two, or three stacked four-helix bundle (4HB) modules. Here, using phylogenomic, structural, and biochemical approaches, we identify a novel monomodular all-helical LBD family, termed 4HB_HD (4HB_HBM-derived), most likely originated from the bimodular all-helical HBM LBD by the loss of its membrane-distal module. A representative family member, PcpI of Pseudomonas putida, binds the plant hormones salicylate and indole-3-acetic acid and mediates chemotaxis toward these compounds. Comparison with the inferred bimodular ancestor, aPcpI, revealed that binds the phytohormones recognized by PcpI via both the membrane-distal and membrane-proximal modules, and additionally recognizes citrate through the membrane-distal module. Despite their distinct chemical structures, these ligands bind to the same site within the membrane-distal module, highlighting structural flexibility as a mechanism for expanding receptor specificity. Structural analyses further show that PcpI-LBD closely superimposes with the membrane-proximal module of aPcpI-LBD and provide a structural rationale for its inability to bind citrate. Together, our results show that modular reduction does not necessarily compromise function and illustrate how rearrangement of ligand-binding modules can drive the microbial evolution of inter-kingdom signal detection. Evolution of monomodular all-helical receptor ligand-binding domains from bimodular ancestors.,Gavira JA, Rico-Jimenez M, Ortega A, Roca A, Krell T, Zhulin IB, Matilla MA Int J Biol Macromol. 2026 Aug 20;382(Pt 1):154135. doi: , 10.1016/j.ijbiomac.2026.154135. PMID:42617770 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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