2WX5

Hexa-coordination of a bacteriochlorophyll cofactor in the Rhodobacter sphaeroides reaction centre

Summary for 2WX5

• Entry DOI: 10.2210/pdb2wx5/pdb
• Related: 1AIG 1AIJ 1DS8 1DV3 1DV6 1E14 1E6D 1F6N 1FNP 1FNQ 1JGW 1JGX 1JGY 1JGZ 1JH0 1K6L 1K6N 1KBY 1L9B 1L9J 1M3X 1MPS 1OGV 1PCR 1PSS 1PST 1QOV 1RG5 1RGN 1RQK 1RVJ 1RY5 1RZH 1RZZ 1S00 1UMX 1YST 1Z9J 1Z9K 2BNP 2BNS 2BOZ 2GMR 2J8C 2J8D 2JIY 2JJ0 2RCR 2UWS 2UWT 2UWU 2UWV 2UWW 2UX3 2UX4 2UX5 2UXJ 2UXK 2UXL 2UXM 4RCR
• Descriptor: REACTION CENTER PROTEIN H CHAIN, CARDIOLIPIN, FE (III) ION, ... (14 entities in total)
• Functional Keywords: photosynthesis, reaction center, membrane protein, photosynthetic reaction center, electron transport, bacteriochlorophyll, iron, membrane, magnesium, transport, chromophore, chlorophyll, metal-binding, transmembrane
• Biological source: RHODOBACTER SPHAEROIDES; More
• Cellular location: Cellular chromatophore membrane; Single-pass membrane protein: P0C0Y7; Cellular chromatophore membrane; Multi-pass membrane protein: P0C0Y8 P0C0Y9
• Total number of polymer chains: 3
• Total formula weight: 104275.12

Authors

Marsh, M.,Frolov, D.,Crouch, L.I.,Fyfe, P.K.,Robert, B.,van Grondelle, R.,Jones, M.R.,Hadfield, A.T. (deposition date: 2009-11-02, release date: 2010-02-09, Last modification date: 2023-12-20)

Primary citation

Frolov, D.,Marsh, M.,Crouch, L.I.,Fyfe, P.K.,Robert, B.,van Grondelle, R.,Hadfield, A.T.,Jones, M.R.
Structural and Spectroscopic Consequences of Hexa-Coordination of a Bacteriochlorophyll Cofactor in the Rhodobacter Sphaeroides Reaction Centre
Biochemistry, 49:1882-, 2010

PubMed Abstract: The structural and functional consequences of changing the coordination state of one of the bacteriochlorophyll (BChl) cofactors in the purple bacterial reaction center have been explored. A combination of steady state spectroscopy and X-ray crystallography was used to demonstrate that mutagenesis of residue 181 of the L-polypeptide from Phe to Arg (FL181R) causes the BChl at the accessory (B(B)) position on the so-called inactive cofactor branch to become hexacoordinated, with no significant changes to the structure of the surrounding protein. This change was accompanied by the appearance of a distinctive absorbance band at 631 nm in the room-temperature absorbance spectrum. The ligand donor was not the Arg side chain but rather an intervening water molecule, and contrary to expectations, the Mg of B(B) did not adopt a more in-plane geometry in response to hexacoordination. The mutation caused a disturbance to the detailed conformation of the BChl macrocycle that manifested in a number of subtle changes to the resonance Raman spectrum. Hexacoordination of B(B) produced a small increase in the lifetime of the excited electronic state of the primary donor bacteriochlorophylls (P*), indicating some disturbance to light-driven energy and/or electron transfer events on the time scale of a few picoseconds after light excitation. The B(B) bacteriochlorophyll returned to a pentacoordinated state in a double mutant where the FL181R mutation was combined with removal of the native axial ligand through mutation of His M182 to Leu. Experimental evidence of hexacoordinated bacteriochlorophylls in the literature on antenna proteins is considered, and possible reasons why hexacoordinated bacteriochlorophylls and chlorophylls appear to be avoided in photosynthetic proteins are discussed.

PubMed: 20112981
DOI: 10.1021/BI901922T

Experimental method

X-RAY DIFFRACTION (2.63 Å)