1DV6

PHOTOSYNTHETIC REACTION CENTER FROM RHODOBACTER SPHAEROIDES IN THE CHARGE-NEUTRAL DQAQB STATE WITH THE PROTON TRANSFER INHIBITOR ZN2+

Summary for 1DV6

• Entry DOI: 10.2210/pdb1dv6/pdb
• Related: 1DV3 1aij 1ds8
• Descriptor: PHOTOSYNTHETIC REACTION CENTER, ZINC ION, BACTERIOCHLOROPHYLL A, ... (11 entities in total)
• Functional Keywords: bacterial photosynthesis, rhodobacter sphaeroides, metal ion binding, cation binding, proton transfer, integral membrane protein, photosynthesis
• Biological source: Rhodobacter sphaeroides; More
• Cellular location: Cellular chromatophore membrane; Multi-pass membrane protein: P02954 P02953; Cellular chromatophore membrane; Single-pass membrane protein: P11846
• Total number of polymer chains: 6
• Total formula weight: 203211.90

Authors

Axelrod, H.L.,Abresch, E.C.,Paddock, M.L.,Okamura, M.Y.,Feher, G. (deposition date: 2000-01-19, release date: 2000-03-08, Last modification date: 2024-02-07)

Primary citation

Axelrod, H.L.,Abresch, E.C.,Paddock, M.L.,Okamura, M.Y.,Feher, G.
Determination of the binding sites of the proton transfer inhibitors Cd2+ and Zn2+ in bacterial reaction centers.
Proc.Natl.Acad.Sci.USA, 97:1542-1547, 2000

PubMed Abstract: The reaction center (RC) from Rhodobacter sphaeroides couples light-driven electron transfer to protonation of a bound quinone acceptor molecule, Q(B), within the RC. The binding of Cd(2+) or Zn(2+) has been previously shown to inhibit the rate of reduction and protonation of Q(B). We report here on the metal binding site, determined by x-ray diffraction at 2.5-A resolution, obtained from RC crystals that were soaked in the presence of the metal. The structures were refined to R factors of 23% and 24% for the Cd(2+) and Zn(2+) complexes, respectively. Both metals bind to the same location, coordinating to Asp-H124, His-H126, and His-H128. The rate of electron transfer from Q(A)(-) to Q(B) was measured in the Cd(2+)-soaked crystal and found to be the same as in solution in the presence of Cd(2+). In addition to the changes in the kinetics, a structural effect of Cd(2+) on Glu-H173 was observed. This residue was well resolved in the x-ray structure-i.e., ordered-with Cd(2+) bound to the RC, in contrast to its disordered state in the absence of Cd(2+), which suggests that the mobility of Glu-H173 plays an important role in the rate of reduction of Q(B). The position of the Cd(2+) and Zn(2+) localizes the proton entry into the RC near Asp-H124, His-H126, and His-H128. Based on the location of the metal, likely pathways of proton transfer from the aqueous surface to Q(B) are proposed.

PubMed: 10677497
DOI: 10.1073/pnas.97.4.1542

Experimental method

X-RAY DIFFRACTION (2.5 Å)