title: Crystal structure of deltarhodopsin-3 from Haloterrigena thermotolerans.
abstract: Deltarhodopsin, a new member of the microbial rhodopsin family, functions as a light-driven proton pump. Here, we report the three-dimensional structure of deltarhodopsin (dR3) from Haloterrigena thermotolerans at 2.7 Å resolution. A crystal belonging to space group R32 (a, b = 111.71 Å, c = 198.25 Å) was obtained by the membrane fusion method. In this crystal, dR3 forms a trimeric structure as observed for bacteriorhodopsin (bR). Structural comparison of dR with bR showed that the inner part (the proton release and uptake pathways) is highly conserved. Meanwhile, residues in the protein-protein contact region are largely altered so that the diameter of the trimeric structure at the cytoplasmic side is noticeably larger in dR3. Unlike bR, dR3 possesses a helical segment at the C-terminal region that fills the space between the AB and EF loops. A significant difference is also seen in the FG loop, which is one residue longer in dR3. Another peculiar property of dR3 is a highly crowded distribution of positively charged residues on the cytoplasmic surface, which may be relevant to a specific interaction with some cytoplasmic component.
authors.affiliation: Department of Physics, Graduate School of Science, Nagoya University, Nagoya, Japan.
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Katsuhide
authors.initials: K
authors.lastname: Mizuno
authors.forename: Yuki
authors.initials: Y
authors.lastname: Murata
authors.forename: Hideaki
authors.initials: H
authors.lastname: Koide
authors.forename: Midori
authors.initials: M
authors.lastname: Murakami
authors.forename: Kunio
authors.initials: K
authors.lastname: Ihara
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Kouyama
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D006216:Halobacteriaceae / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D025604:Rhodopsins, Microbial / Q000737:chemistry*
chemical_list: D011994:Recombinant Proteins; D025604:Rhodopsins, Microbial
keywords: X-ray crystallography; membrane protein; proton pump; retinal protein; rhodopsin