Gai W Z, Sun S M, Ding Y Z, Freedman J A, Chan S H
Biology Department, Syracuse University, New York 13244.
Arch Biochem Biophys. 1988 Nov 1;266(2):628-38. doi: 10.1016/0003-9861(88)90296-2.
Two monoclonal lines of antibodies were isolated with specificities against the amino half of Subunit IV of beef heart cytochrome oxidase. The lines had nonoverlapping epitopes. Both bound to the matrix face of membranous oxidase, neither bound to the cytoplasmic face. One line (QA4/C4) stimulated electron transfer in soluble or membranous oxidase, while the other (QA4) inhibited that activity by both oxidase preparations. These effects on electron transfer activity were not altered by the inclusion or omission of detergent. ATP depressed the binding of either antibody to either soluble or membranous oxidase. In the absence of ATP, QA4/C4 stimulated electron transfer only in the high affinity phase of cytochrome c oxidation (with decreased KM and increased Vmax), causing slight inhibition in the low affinity phase (with decreased KM). In the presence of ATP, QA4/C4 abolished the high affinity phase, but did not alter the ATP influence on the low affinity phase. In the absence of ATP, antibodies of line QA4 abolished the low affinity phase, leaving a high affinity phase similar to that induced by ATP. In the presence of ATP, QA4 abolished the high affinity phase, leaving a low affinity phase similar to that seen with ATP alone. This behavior is consistent with the dissection of two catalytic sites for cytochrome c and more than one ATP affector site.
分离出了两种单克隆抗体株，它们对牛心细胞色素氧化酶亚基IV的氨基端具有特异性。这两种株系具有不重叠的表位。它们都与膜状氧化酶的基质面结合，均不与胞质面结合。一个株系（QA4/C4）能刺激可溶性或膜状氧化酶中的电子传递，而另一个株系（QA4）则抑制这两种氧化酶制剂的该活性。这些对电子传递活性的影响不会因加入或不加入去污剂而改变。ATP降低了两种抗体与可溶性或膜状氧化酶的结合。在没有ATP的情况下，QA4/C4仅在细胞色素c氧化的高亲和力阶段刺激电子传递（KM降低，Vmax增加），在低亲和力阶段引起轻微抑制（KM降低）。在有ATP的情况下，QA4/C4消除了高亲和力阶段，但未改变ATP对低亲和力阶段的影响。在没有ATP的情况下，QA4株系的抗体消除了低亲和力阶段，留下了类似于由ATP诱导的高亲和力阶段。在有ATP的情况下，QA4消除了高亲和力阶段，留下了类似于仅用ATP时所见的低亲和力阶段。这种行为与细胞色素c的两个催化位点以及不止一个ATP作用位点的剖析是一致的。
