THE TIME-COURSE OF CA-2+ EXCHANGE WITH CALMODULIN, TROPONIN, PARVALBUMIN, AND MYOSIN IN RESPONSE TO TRANSIENT INCREASES IN CA-2+
THE TIME-COURSE OF CA-2+ EXCHANGE WITH CALMODULIN, TROPONIN, PARVALBUMIN, AND MYOSIN IN RESPONSE TO TRANSIENT INCREASES IN CA-2+
复制标题
DOI：
10.1016/s0006-3495(81)84868-0
复制
发表时间：
1981-01-01
影响因子：
3.4
通讯作者：
POTTER, JD
中科院分区：
文献类型：
--
作者：
ROBERTSON, SP;JOHNSON, JD;POTTER, JD
模拟了 Ca2+ 与钙调蛋白、肌钙蛋白、小白蛋白和肌球蛋白结合的时间过程，以响应游离肌浆 Ca 离子浓度 (pCa) 的瞬时增加。使用一个简单的数学表达式来描述每个 pCa 瞬变，其形状和持续时间在质量上与体内发生的相似。这些计算假设所有单独的金属结合位点都是非相互作用的，并且 Ca2+ 和 Mg2+ 竞争性地结合到肌钙蛋白、小白蛋白和肌球蛋白的 Ca2+-Mg2+ 位点。 Ca2+-Mg2+位点与Ca2+的饱和百分比响应于存在2.5倍的每个pCa瞬变而变化非常小。 10-3 M Mg2+。分析表明，这些部位的 Ca2+ 含量是近期肌肉活动强度和频率的衡量标准，因为重复刺激时，这些部位的 Ca2+ 占有率可能会发生巨大变化。每个 pCa 瞬变都会引起与肌钙蛋白和钙调蛋白的 Ca2+ 特异性位点结合的 Ca2+ 量的大幅快速变化。只有 Ca2+ 特异性类型的位点才能充当肌肉中的快速 Ca2+ 调节位点。响应于各种类型的 pCa 瞬变，与这些位点结合的 Ca2+ 总量的波动进一步表明，在体内仅.apprx。总稳态肌原纤维 Ca2+ 结合能力的 1/2-1/3 在任何单一瞬态期间交换 Ca2+。
The time-course of Ca2+ binding to calmodulin, troponin, parvalbumin and myosin in response to trains of transient increases in the free myoplasmic Ca ion concentration (pCa) was modeled. A simple mathematical expression was used to describe each pCa transient, the shape and duration of which is qualitatively similar to those thought to occur in vivo. These calculations assumed that all the individual metal binding sites are noninteracting and that Ca2+ and Mg2+ bind competitively to the Ca2+-Mg2+ sites of troponin, parvalbumin and myosin. The percent saturation of the Ca2+-Mg2+ sites with Ca2+ changed very little in response to each pCa transient in the presence of 2.5 .times. 10-3 M Mg2+. Analysis suggests that the Ca2+ content of these sites is a measure of the intensity and frequency of recent muscle activity because large changes in the Ca2+ occupancy of these sites can occur with repeated stimulation. Large rapid changes in the amount of Ca2+ bound to the Ca2+-specific sites of troponin and calmodulin are induced by each pCa transient. Only sites of the Ca2+-specific type can act as rapid Ca2+-regulatory sites in muscle. Fluctuation in the total amount of Ca2+ bound to these sites in response to various types of pCa transients further suggests that in vivo only .apprx. 1/2-1/3 of the total steady-state myofibrillar Ca2+-binding capacity exchanges Ca2+ during any single transient.