Ubiquinone binding, ubiquinone exclusion, and detailed cofactor conformation in a mutant bacterial reaction center

McAuley, KE, Fyfe, PK, Ridge, JP, Cogdell, RJ, Isaacs, NW and Jones, MR (2000) Ubiquinone binding, ubiquinone exclusion, and detailed cofactor conformation in a mutant bacterial reaction center. Biochemistry, 39 49: 15032-15043. doi:10.1021/bi000557r


Author McAuley, KE
Fyfe, PK
Ridge, JP
Cogdell, RJ
Isaacs, NW
Jones, MR
Title Ubiquinone binding, ubiquinone exclusion, and detailed cofactor conformation in a mutant bacterial reaction center
Journal name Biochemistry   Check publisher's open access policy
ISSN 0006-2960
Publication date 2000-12-01
Year available 2000
Sub-type Article (original research)
DOI 10.1021/bi000557r
Open Access Status DOI
Volume 39
Issue 49
Start page 15032
End page 15043
Total pages 12
Place of publication WASHINGTON
Publisher AMER CHEMICAL SOC
Language eng
Abstract The X-ray crystal structure of a Rhodobacter sphaeroides reaction center with the mutation Ala M260 to Trp (AM260W) has been determined. Diffraction data were collected that were 97.6% complete between 30.0 and 2.1 Angstrom resolution. The electron density maps confirm the conclusions of a previous spectroscopic study, that the Q(A) ubiquinone is absent from the AM260W reaction center (Ridge, J. P., van Brederode, M. E., Goodwin, M. G., van Grondelle, R., and Jones, M. R. (1999) Photosynthesis Res. 59, 9-26). Exclusion of the Q(A) ubiquinone caused by the AM260W mutation is accompanied by a change in the packing of amino acids in the vicinity of the Q(A) Site that form part of a loop that connects the DE and E helices of the M subunit. This repacking minimizes the volume of the cavity that results from the exclusion of the Q(A) ubiquinone, and further space is taken up by a feature in the electron density maps that has been modeled as a chloride ion. An unexpected finding is that the occupancy of the Q(B) Site by ubiquinone appears to be high in the AM260W crystals, and as a result the position of the Q(B) ubiquinone is well-defined. The high quality of the electron density maps also reveals more precise information on the detailed conformation of the reaction center carotenoid, and we discuss the possibility of a bonding interaction between the methoxy group of the carotenoid and residue Trp M75. The conformation of the 2-acetyl carbonyl group in each of the reaction center bacteriochlorins is also discussed.
Keyword Photosynthetic Reaction-Center
Rhodobacter-Sphaeroides R-26
X-Ray-Diffraction
Rhodopseudomonas-Viridis
Photoactive Bacteriopheophytin
Electronic-Structure
Crystal-Structures
Triple-Resonance
Refinement
Bacteriochlorophyll
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
Collection: ResearcherID Downloads - Archived
 
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