Quinone reduction via secondary B-branch electron transfer in mutant bacterial reaction centers

被引:58
作者
Laible, PD [1 ]
Kirmaier, C
Udawatte, CSM
Hofman, SJ
Holten, D
Hanson, DK
机构
[1] Argonne Natl Lab, Biosci Div, Argonne, IL 60439 USA
[2] Washington Univ, Dept Chem, St Louis, MO 63130 USA
关键词
D O I
10.1021/bi026959b
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Symmetry-related branches of electron-transfer cofactors-initiating with a primary electron donor (P) and terminating in quinone acceptors (Q)-are common features of photosynthetic reaction centers (RC). Experimental observations show activity of only one of them-the A branch-in wild-type bacterial RCs. In a mutant RC, we now demonstrate that electron transfer can occur along the entire, normally inactive B-branch pathway to reduce the terminal acceptor Q(B) on the time scale of nanoseconds. The transmembrane charge-separated state P(+)Q(B)(-) is created in this manner in a Rhodobacter capsulatus RC containing the F(L181)Y-Y(M208)F-L(M212)H-W(M250)V mutations (YFHV). The W(M250)V mutation quantitatively blocks binding of Q(A), thereby eliminating Q(B) reduction via the normal A-branch pathway. Full occupancy of the Q(B) site by the native UQ(10) is ensured (without the necessity of reconstitution by exogenous quinone) by purification of RCs with the mild detergent, Deriphat 160-C. The lifetime of P(+)Q(B)(-) in the YFHV mutant RC is >6 s (at pH 8.0, 298 K). This charge-separated state is not formed upon addition of competitive inhibitors of Q(B) binding (terbutryn or stigmatellin). Furthermore, this lifetime is much longer than the value of similar to1-1.5 s found when P(+)Q(B)(-) is produced in the wild-type RC by A-side activity alone. Collectively, these results demonstrate that P(+)Q(B)(-) is formed solely by activity of the B-branch carriers in the YFHV RC. In comparison, P(+)Q(B)(-) can form by either the A or B branches in the YFH RC, as indicated by the biexponential lifetimes of similar to1 and similar to6-10 s. These findings suggest that P(+)Q(B)(-) states formed via the two branches are distinct and that P(+)Q(B)(-) formed by the B side does not decay via the normal (indirect) pathway that utilizes the A-side cofactors when present. These differences may report on structural and energetic factors that further distinguish the functional asymmetry of the two cofactor branches.
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页码:1718 / 1730
页数:13
相关论文
共 92 条
[81]  
TIEDE DM, 1992, PHOTOSYNTHETIC BACTE, V2, P341
[82]  
Turzó K, 1999, ISR J CHEM, V39, P447, DOI 10.1002/ijch.199900050
[83]   Cu2+ site in photosynthetic bacterial reaction centers from Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas viridis [J].
Utschig, LM ;
Poluektov, O ;
Schlesselman, SL ;
Thurnauer, MC ;
Tiede, DM .
BIOCHEMISTRY, 2001, 40 (20) :6132-6141
[84]   COMPARATIVE-STUDY OF REACTION CENTERS FROM PURPLE PHOTOSYNTHETIC BACTERIA - ISOLATION AND OPTICAL SPECTROSCOPY [J].
WANG, S ;
LIN, S ;
LIN, X ;
WOODBURY, NW ;
ALLEN, JP .
PHOTOSYNTHESIS RESEARCH, 1994, 42 (03) :203-215
[85]   CHARACTERIZATION OF RHODOPSEUDOMONAS-CAPSULATA [J].
WEAVER, PF ;
WALL, JD ;
GEST, H .
ARCHIVES OF MICROBIOLOGY, 1975, 105 (03) :207-216
[86]  
Woodbury N. W., 1995, Anoxygenic Photosynthetic Bacteria, P527
[87]   RADICAL-PAIR ENERGETICS AND DECAY MECHANISMS IN REACTION CENTERS CONTAINING ANTHRAQUINONES, NAPHTHOQUINONES OR BENZOQUINONES IN PLACE OF UBIQUINONE [J].
WOODBURY, NW ;
PARSON, WW ;
GUNNER, MR ;
PRINCE, RC ;
DUTTON, PL .
BIOCHIMICA ET BIOPHYSICA ACTA, 1986, 851 (01) :6-22
[88]   Exploring the energy landscape for QA- to QB electron transfer in bacterial photosynthetic reaction centers:: Effect of substrate position and tail length on the conformational gating step [J].
Xu, Q ;
Baciou, L ;
Sebban, P ;
Gunner, MR .
BIOCHEMISTRY, 2002, 41 (31) :10021-10025
[89]   Exploring the energy profile of the QA- to QB electron transfer reaction in bacterial photosynthetic reaction centers:: pH dependence of the conformational gating step [J].
Xu, Q ;
Gunner, MR .
BIOCHEMISTRY, 2002, 41 (08) :2694-2701
[90]   CHROMOSOMAL DELETION AND PLASMID COMPLEMENTATION OF THE PHOTOSYNTHETIC REACTION CENTER AND LIGHT-HARVESTING GENES FROM RHODOPSEUDOMONAS-CAPSULATA [J].
YOUVAN, DC ;
ISMAIL, S ;
BYLINA, EJ .
GENE, 1985, 38 (1-3) :19-30