Evidence that Ala M260 is hydrogen-bonded to the reduced primary acceptor quinone QA−. in reaction centers of Rb. sphaeroides

Spoyalov, A.P.; Hulsebosch, R.J.; Shochat, S.; Gast, P.; Hoff, A.J. (1996)

Article / Letter to editor

The binding of the primary quinone anion radical Q(A)(-.) in reaction centers (RCs) of Rhodobacter (Rb.) sphaeroides species was investigated with electron spin echo envelope modulation (ESEEM). The ESEEM spectra, at two microwave frequencies, of Zn-substituted RCs of Rb. sphaeroides R26 showed interactions of the unpaired electron of Q(A)(-.) with two nitrogen nuclei in the protein matrix. From an analysis of the experimental data the nitrogen nuclear quadrupole resonance parameters were determined: e(2)qQ/h = 1.52 MHz, eta = 0.82 and e(2)qQ/h = 3.04 MHz, eta = 0.66, which are assigned to the N-14(8(1))-H group of His M219 and the peptide N-14 of Ala M260, The ESEEM spectrum of Q(A)(-.) in reaction centers of the Rb, sphaeroides mutant W(M252)Y shows that the nitrogen of Trp M252 is not interacting with Q(A)(-.), that of the mutant H(M266)C shows that manipulating the Fe binding site strongly affects the Q(A)-binding site.

• All authors: Spoyalov, A.P.; Hulsebosch, R.J.; Shochat, S.; Gast, P.; Hoff, A.J.
• Date: 1996-12-20
• Journal: Chemical Physics Letters
• Volume: 263
• Issue: 5
• Pages: 715 - 720
• DOI: doi:10.1016/S0009-2614(96)01255-9