9WXR

sensory rhodopsin I with its cognate transducer HtrI

Summary for 9WXR

• Entry DOI: 10.2210/pdb9wxr/pdb
• EMDB information: 66355
• Descriptor: Rhodopsin,Chemotaxis protein, RETINAL (2 entities in total)
• Functional Keywords: sensory rhodopsin, transducer, hamp domain, phototaxis, signaling protein
• Biological source: Haloarcula taiwanensis; More
• Total number of polymer chains: 2
• Total formula weight: 78093.61

Authors

Lim, G.Z.,Lin, Y.E.,Wu, Y.M.,Chen, P.C.,Fu, H.Y.,Yang, C.S. (deposition date: 2025-09-25, release date: 2026-04-22, Last modification date: 2026-04-29)

Primary citation

Lim, G.Z.,Lin, Y.E.,Chen, P.C.,Fu, H.Y.,Yang, C.S.
Cryo-EM structure of the SRI-HtrI complex reveals the cytoplasmic coupling in an archaeal phototaxis system.
Nat Commun, 2026

PubMed Abstract: Sensory rhodopsins (SRs) in haloarchaea form complexes with their cognate transducers (Htrs) to produce wavelength-specific phototactic responses, yet similar architectures mediate distinct behaviors: SRI mediates attraction, SRII drives repulsion, whereas SRM modulates both responses. Until now, structural insight was limited to the Natronomonas pharaonis SRII-HtrII system in a truncated form, without a full-length counterpart for comparison. Moreover, NpHtrII is distinct among HtrII transducers in lacking the large periplasmic domain retained in homologs from Halobacterium salinarum, Haloarcula marismortui and Haloarcula taiwanensis, leaving the canonical SR-Htr architecture unknown. Here, we report the cryo-EM structure of the Haloarcula taiwanensis SRI-HtrI complex, providing a near native, non-crystallized view of a full-length SR-Htr dimer with the cytoplasmic HAMP1 domain resolved. The structure reveals the intact homodimeric receptor-transducer assembly and visualizes the interface between the helix G (Arg215), SRI E-F loop (Pro154), and HtrI HAMP1. These findings fill the long-standing structural gap for a canonical SR-Htr complex and establish a framework for conserved receptor-transducer coupling across archaeal phototaxis systems.

PubMed: 41991530
DOI: 10.1038/s41467-026-72092-6

Experimental method

ELECTRON MICROSCOPY (4.9 Å)