2boz

From Proteopedia

Revision as of 16:44, 18 December 2007

PHOTOSYNTHETIC REACTION CENTER MUTANT WITH GLY M203 REPLACED WITH LEU

Overview

The role of a water molecule (water A) located between the primary, electron donor (P) and first electron acceptor bacteriochlorophyll (B(A)), in the purple bacterial reaction center was investigated by mutation of, glycine M203 to leucine (GM203L). The x-ray crystal structure of the, GM203L reaction center shows that the new leucine residue packs in such a, way that water A is sterically excluded from the complex, but the, structure of the protein-cofactor system around the mutation site is, largely undisturbed. The results of absorbance and resonance Raman, spectroscopy were consistent with either the removal of a hydrogen bond, interaction between water A and the keto carbonyl group of B(A) or a, change in the local electrostatic environment of this carbonyl group., Similarities in the spectroscopic properties and x-ray crystal structures, of reaction centers with leucine and aspartic acid mutations at the M203, position suggested that the effects of a glycine to aspartic acid, substitution at the M203 position can also be explained by steric, exclusion of water A. In the GM203L mutant, loss of water A was, accompanied by an approximately 8-fold slowing of the rate of decay of the, primary donor excited state, indicating that the presence of water A is, important for optimization of the rate of primary electron transfer., Possible functions of this water molecule are discussed, including a, switching role in which the redox potential of the B(A) acceptor is, rapidly modulated in response to oxidation of the primary electron donor.

About this Structure

2BOZ is a Protein complex structure of sequences from Rhodobacter sphaeroides with FE, PO4, LDA, D10, BCL, BH1, U10 and SPN as ligands. Known structural/functional Site: . Full crystallographic information is available from OCA.

Reference

Strong effects of an individual water molecule on the rate of light-driven charge separation in the Rhodobacter sphaeroides reaction center., Potter JA, Fyfe PK, Frolov D, Wakeham MC, van Grondelle R, Robert B, Jones MR, J Biol Chem. 2005 Jul 22;280(29):27155-64. Epub 2005 May 20. PMID:15908429

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