Wikström M, Saari H
Biochim Biophys Acta. 1975 Nov 11;408(2):170-9. doi: 10.1016/0005-2728(75)90009-2.
Ca2+ induces a red shift in the absorption spectrum of ferrocytochrome a when added to uncoupled mitochondria, sub-mitochondrial particles or isolated cytochrome aa3. The shift is identical within experimental error to the previously reported energy-linked shift in intact mitochondria (Wikström, M. K. F. (1972), Biochim. Biophys. Acta 283, 385-390). One mol of calcium produces the shift in one mole of cytochrome a, the KD being approx. 20-30 muM. The calcium-induced shift is readily reversed by chelating agents such as EDTA, ethyleneglycol-bis-(beta-aminoethyl ether)N,N'-tetraacetic acid (EGTA) and ATP and is insensitive to uncoupling agents and inhibitors of calcium transport (La3+ and ruthenium red). It is shown that the binding site for calcium that is responsible for the spectral shift is located on the outside of the permeability barrier of the mitochondrial cristae membrane. It is proposed that calcium simulates the energy-linked shift in cytochrome a by binding to a site of cytochrome aa3 that is occupied by protons in energized mitochondria and that is located at the external surface of the mitochondrial membrane.
当向解偶联的线粒体、亚线粒体颗粒或分离的细胞色素aa3中添加Ca2+时，它会诱导亚铁细胞色素a的吸收光谱发生红移。在实验误差范围内，这种红移与先前报道的完整线粒体中的能量相关红移相同（维克斯特伦，M.K.F.（1972年），《生物化学与生物物理学报》283，385 - 390）。一摩尔钙会使一摩尔细胞色素a发生红移，解离常数约为20 - 30微摩尔。钙诱导的红移很容易被螯合剂如乙二胺四乙酸（EDTA）、乙二醇双（β - 氨基乙基醚）N，N' - 四乙酸（EGTA）和ATP逆转，并且对解偶联剂和钙转运抑制剂（镧离子和钌红）不敏感。结果表明，负责光谱红移的钙结合位点位于线粒体内嵴膜通透性屏障的外侧。有人提出，钙通过与细胞色素aa3的一个位点结合来模拟细胞色素a中的能量相关红移，该位点在有能量的线粒体中被质子占据，且位于线粒体外表面。
