Comparison of turnover of several myofibrillar proteins and critical evaluation of double isotope method.
Comparison of turnover of several myofibrillar proteins and critical evaluation of double isotope method.
复制标题
几种肌原纤维蛋白周转率的比较和双同位素法的严格评价。
DOI：
10.1016/s0021-9258(17)40409-1
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发表时间：
1977
期刊：
影响因子：
--
通讯作者：
M. Rabinowitz
中科院分区：
文献类型：
--
作者：
R. Zak;A. Martin;G. Prior;M. Rabinowitz
大鼠心肌中几种肌原纤维蛋白的周转，即肌凝蛋白重链、轻链、肌动蛋白、原肌凝蛋白和cap α。采用双同位素技术和电泳分离蛋白中亮氨酸的比放射性测定两种方法对-肌动蛋白进行了比较。通过对前体-产物关系的计算机分析，评价了双同位素方法的灵敏度。在此分析的基础上，我们选择的实验条件，最大限度地区分蛋白质周转率可以得到。此外，通过计算机构造的曲线将实验得出的双同位素比值转换为半衰期。各肌原纤维蛋白的周转率关系如下：肌球蛋白重链= ..-肌动蛋白=原肌凝蛋白>肌动蛋白>轻链1 =轻链2当测量亮氨酸并入单个肌原纤维蛋白的速率时，获得了类似的关系。轻链1和轻链2比放射性与肌球蛋白重链比放射性随时间变化。给标后10 min轻链1/重链= 0.43，轻链2/重链= 0.38。4 d后，比值分别为0.71和0.77。肌凝蛋白重链和轻链的特定放射性随时间的收敛与轻链的大分子前体的存在是一致的，这些轻链尚未组装成完整的肌凝蛋白分子。
The turnover of several myofibrillar proteins in the rat myocardium, namely, myosin heavy chain, light chains, actin, tropomyosin, and ..cap alpha..-actinin, was compared by two methods: the double isotope technique and determination of the specific radioactivity of leucine in electrophoretically separated proteins. The sensitivity of the double isotope method was evaluated by computer analysis of the precursor-product relationship. On the basis of this analysis, we selected experimental conditions whereby maximum discrimination between protein turnover rates could be obtained. In addition, experimentally derived double isotope ratios were converted into half-lives by means of a computer-constructed curve. The turnover rates of individual myofibrillar proteins were related as follows: myosin heavy chain = ..cap alpha..-actinin = tropomyosin>actin>light chain 1 = light chain 2. A similar relationship was obtained when the rate of leucine incorporation into individual myofibrillar proteins was measured. The ratio of light chain 1 and light chain 2 specific radioactivity to that of myosin heavy chain changed with time, however. The ratios were light chain 1/heavy chain = 0.43, light chain 2/heavy chain = 0.38 10 min after administration of label. Four days later, the ratios were 0.71 and 0.77, respectively. The convergence of the specific radioactivities of heavy and light chains of myosin with time is consistent with the existence of a macromolecular precursor of light chains that has not yet been assembled into a complete myosin molecule.