Shift of the Special Pair Redox Potential: Electrostatic Energy Computations of Mutants of the Reaction Center from Rhodobacter sphaeroides

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• 作者：I. Muegge ; J. Apostolakis ; U. Ermler ; G. Fritzsch ; W. Lubitz ; and E. W. Knapp
• 刊名：Biochemistry
• 出版年：1996
• 出版时间：June 25, 1996
• 年：1996
• 卷：35
• 期：25
• 页码：8359 - 8370
• 全文大小：520K
• 年卷期：v.35,no.25(June 25, 1996)
• ISSN：1520-4995

文摘

Shifts of the special pair redox potential of the photosyntheticreaction center of Rhodobactersphaeroides are considered for several point mutations [Lin, X.,Murchison, H. A., Nagarijan, V., Parson,W. W., Allen, J. P., & Williams, J. C. (1994) Proc.Natl. Acad. Sci.U.S.A. 91, 10265-10269]in theneighborhood of the special pair. The shifts are calculated fromelectrostatic energies by solving Poisson'sequation for energy-minimized structures of the reaction center.Different conditions for the evaluationof the electrostatic energy are probed. To test the influence ofthe hydrogen bonding at the acetyl groupsof the special pair, the orientation and torsion potential of theacetyl groups are varied. The calculatedshifts of the midpoint potential of double and triple mutants canapproximately be obtained from thecorresponding shifts of the single point mutations. The calculatedshifts agree with the measured valuesfor all single and double mutants considered. However, a cleardecision between different acetyl groupconformations was only possible for the mutants HF(L168) andHF(L168) + LH(L131) where the calculatedshifts of the redox potential agree with experiments only if the acetyloxygen atom at D_M points towardthe Mg²⁺ ion of D_L. This is corroboratedby computations of the interaction energy of the acetylgroupat D_M, which adopts a lower value in the wild-type reactioncenter if its oxygen atom is bonded to theMg²⁺ ion of D_L.