ZINC IONS INHIBIT THE Q(P) CENTER OF BOVINE HEART MITOCHONDRIAL BC(1) COMPLEX BY BLOCKING A PROTONATABLE GROUP
ZINC IONS INHIBIT THE Q(P) CENTER OF BOVINE HEART MITOCHONDRIAL BC(1) COMPLEX BY BLOCKING A PROTONATABLE GROUP
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DOI：
10.1074/jbc.270.42.25001
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发表时间：
1995-10-20
影响因子：
4.8
通讯作者：
VONJAGOW, G
中科院分区：
文献类型：
--
作者：
LINK, TA;VONJAGOW, G
锌离子可逆地抑制牛心脏bc(1)络合物，在pH大于或等于7.0时，抑制常数K-I为10(-7)M。锌的结合强度至少是其他金属离子结合强度的10倍。在[Zn2+] bb50 μ m浓度下，观察到对泛氢醌细胞色素c氧化还原酶活性的基本完全抑制。锌不影响底物、泛氢醌或细胞色素c的K-m，但锌通过Q(P)中心抑制泛氢醌对细胞色素的还原。使用Zn-65的放射性结合试验显示，在pH = 7.0时，每个bc(1)配合物有一个高亲和力结合位点，K-D小于或等于10(-7)M，另外还有3-4个低亲和力结合位点（K-D bbb2 × 10(-6) M）。锌结合不依赖于高电位链（铁硫蛋白和细胞色素c(1)）的氧化还原状态。与Lorusso等人（Lorusso， M, Cocco， T., Sardanella, a . M., Minuto， M., Bonomi， F., and Papa， S.(1991)）最近的报告相反，锌与fe -s -贫bc(1)复合物的结合强度是前者的3倍，表明锌结合位点不在“Rieske”铁硫蛋白上。中国生物医学工程学报，1997,18(5):555-561。锌与一个对锌和质子具有相同亲和力的位点结合。我们得出结论，锌结合位点靠近bc(1)配合物的一个可质子化基团，pK(a) = 7.2，这是以前没有发现的。我们认为这个基团是bc(1)配合物对苯二酚氧化中心质子通道的一部分。
Bovine heart bc(1) complex is reversibly inhibited by zinc ions with an inhibition constant K-I of 10(-7) M at pH greater than or equal to 7.0. Binding of zinc is at least a factor of 10 tighter than binding of any other metal ion tested. Essentially complete inhibition of ubihydroquinonecytochrome c oxidoreductase activity is observed at concentrations of [Zn2+] > 5 mu M. Zinc does not affect the K-m for the substrates, ubihydroquinone or cytochrome c, but zinc inhibits reduction of the cytochromes by ubihydroquinone through the Q(P) center. A radioactive binding assay using Zn-65 revealed one high affinity binding site per bc(1) complex with K-D less than or equal to 10(-7) M at pH = 7.0 and 3-4 additional low affinity binding sites (K-D > 2 x 10(-6) M). Zinc binding does not depend on the redox state of the high potential chain (iron sulfur protein and cytochrome c(1)). Zinc binds 3 times tighter to Fe-S-depleted bc(1) complex indicating that the zinc binding site is not on the ''Rieske'' iron-sulfur protein in contrast to a recent report by Lorusso et al, (Lorusso, M,, Cocco, T., Sardanella, A. M., Minuto, M., Bonomi, F., and Papa, S. (1991) Eur. J. Biochem. 197, 555-561). Zinc binds to a site which has the same affinity for zinc as for protons. We conclude that the zinc binding site is close to a protonatable group of the bc(1) complex with pK(a) = 7.2 which has not been identified previously. We propose that this group is part of the proton channel at the hydroquinone oxidation center of the bc(1) complex.