Dean R T, Thomas S M, Garner A
Biochem J. 1986 Dec 1;240(2):489-94. doi: 10.1042/bj2400489.
A flux of hydroxyl radicals generated by gamma-irradiation can fragment monoamine oxidase in the membrane of submitochondrial particles. This fragmentation can be inhibited by mannitol and in addition is more extensive in monoamine oxidase preparations that have been depleted of lipid. This latter observation is consistent with the higher yields of fragmentation induced by hydroxyl radicals in soluble proteins in the absence of added lipids. In the absence of oxygen, gamma-irradiation of submitochondrial particles leads to cross-linking reactions. A flux of hydroperoxyl radicals also causes fragmentation, whereas one of superoxide is virtually inactive in this respect. The irradiation of submitochondrial particles leads in addition to the accumulation of products of lipid peroxidation. When these irradiated preparations are exposed to ferrous or cupric salts a further fragmentation of monoamine oxidase ensues, especially at acid pH. These transition-metal-catalysed reactions do not occur with irradiated preparations depleted of lipid, and the post-irradiation protein modifications are concomitant with further lipid peroxidation. The data indicate roles for lipid radicals in both fragmentation and cross-linking reactions of proteins in biological membranes. These reactions may have an important bearing on control of protein activity and of protein turnover in membranes.
γ射线辐照产生的羟自由基通量可使亚线粒体颗粒膜中的单胺氧化酶发生片段化。甘露醇可抑制这种片段化，此外，在脂质已被去除的单胺氧化酶制剂中，这种片段化更为广泛。后一观察结果与在没有添加脂质的情况下，羟自由基诱导可溶性蛋白质产生更高片段化产率相一致。在无氧条件下，γ射线辐照亚线粒体颗粒会导致交联反应。氢过氧自由基通量也会引起片段化，而超氧自由基在这方面几乎没有活性。亚线粒体颗粒的辐照还会导致脂质过氧化产物的积累。当这些辐照制剂暴露于亚铁盐或铜盐时，单胺氧化酶会进一步片段化，尤其是在酸性pH条件下。这些过渡金属催化的反应在脂质已被去除的辐照制剂中不会发生，辐照后蛋白质的修饰与进一步的脂质过氧化同时发生。数据表明脂质自由基在生物膜中蛋白质的片段化和交联反应中均发挥作用。这些反应可能对膜中蛋白质活性的控制和蛋白质周转具有重要影响。
