Pathway of proton transfer in bacterial reaction centers: role of aspartate-L213 in proton transfers associated with reduction of quinoneto dihydroquinone.
Pathway of proton transfer in bacterial reaction centers: role of aspartate-L213 in proton transfers associated with reduction of quinoneto dihydroquinone.
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细菌反应中心的质子转移途径：天冬氨酸-L213 在与醌二氢醌还原相关的质子转移中的作用。
DOI：
10.1021/bi00169a015
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发表时间：
1994
期刊：
影响因子：
2.9
通讯作者：
Okamura,MY
中科院分区：
文献类型：
--
作者：
Paddock,ML;Rongey,SH;McPherson,PH;Juth,A;Feher,G;Okamura,MY
摘要：用具有不同质子供体性质的残基定点替换Asp，研究了Asp-L213在球形红杆菌反应中心(RC)质子转移到还原醌QB中的作用。与天然反应中心(Qa‘Qb™+2H+-*·QQbHZ)相比，位于L213的Asn、Leu、Thr和Ser的反应中心显著降低了质子耦合电子转移[&ab(2)]和与第二电子还原相关的质子摄取速率(Qa’Qb RCS+2H+-*·QQbHZ)。在L213含有Glu的RCS显示出比其他突变体RCS更快的电子和质子转移速率(~90倍)，但与天然RCS相比仍降低(~70倍)。这些结果表明，当羧酸占据L213位时，&Ab(2)较大，这与Asp-L213是质子转移链成分的说法一致。用Glu和Asp在L213处观察到的减少的&ab(2)表明，除了其质子转移能力外，Aspat L213对质子转移也是重要的。Glu-L213比Asp-L213(Pata<；4)具有更高的表观电荷(p/sta>；7)，电荷复合速率(D+QaQb~*·
Revised Manuscript Received November 4, 1993® abstract: The role of Asp-L213 in proton transfer to reduced quinone Qb in the reaction center (RC) from Rhodobacter sphaeroides was studied by site-directed replacement of Asp with residues having different proton donor properties. Reaction centers (RCs) with Asn, Leu, Thr, and Ser at L213 had greatly reduced (~ 6000-fold) proton-coupled electron transfer [&ab (2)] and proton uptake rates associated with the second electron reduction of Qb (Qa'Qb™+ 2H+-*·QaQbHz) compared to native RCs. RCs containing Glu at L213 showed faster (~ 90-fold) electron and proton transfer rates than the other mutant RCs but were still reduced (~ 70-fold) compared with native RCs. These results show that &Ab (2) is larger when a carboxylic acid occupies the L213 site, consistent with the proposal that Asp-L213 is a component of a proton transfer chain. The reduced &ab (2) observed with Glu versus Asp at L213 suggests that Aspat L213 is important for proton transfer for some other reason in addition toits proton transfer capabilities. Glu-L213 is estimated to have a higher apparent(p/sTa> 7) than Asp-L213 (pATa< 4), as indicated by the slower rate of charge recombination (D+ QaQb~~*·