Phosphorylation-dephosphorylation of the 18,000-dalton light chain of myosin during the contraction-relaxation cycle of frog muscle.
Phosphorylation-dephosphorylation of the 18,000-dalton light chain of myosin during the contraction-relaxation cycle of frog muscle.
复制标题
青蛙肌肉收缩-舒张周期期间肌球蛋白 18,000 道尔顿轻链的磷酸化-去磷酸化。
DOI：
10.1016/s0021-9258(18)50806-1
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发表时间：
1979
期刊：
影响因子：
--
通讯作者：
M. Kushmerick
中科院分区：
文献类型：
--
作者：
K. Bárány;M. Bárány;J. Gillis;M. Kushmerick
肌球蛋白的l &000-道尔顿轻链在蛙肌收缩和舒张周期中发生磷酸化和去磷酸化。轻链磷酸化的程度是收缩早期刺激持续时间的函数。在0 ℃时，分别刺激200和500 ms的肌肉中，0.14和0.22 mol [S2 P]磷酸盐/m01轻链的转移量分别为最大强直张力的40%和80%。在不同温度下强直化的几秒钟期间，转移了0.2至0.3摩尔的[3eP]磷酸盐，而电刺激20至30秒或咖啡因处理20分钟导致0.35至0.4摩尔的[3”P]磷酸盐的酯化。这种磷酸化的增加似乎与持续存在的肌浆Ca 2+在激活水平，即，> 10 -8 M。轻链磷酸化在刺激的半腱肌肌肉拉伸超过点的重叠的厚和薄的细丝是相同的肌肉刺激在标准的休息长度时，刺激的时间是至少3秒。数据表明，肌肉本身的刺激而不是机械事件引发磷酸化。轻链去磷酸化发生在肌肉活动的松弛期。短暂强直后，去磷酸化大致跟随松弛。在较长时间的强直后，松弛发生在去磷酸化之前。体外实验表明，CaZ+的情况下所需的轻链去磷酸化和磷酰基基团不翻转活性肌原纤维ATP酶。轻链磷酸化可能通过提供驱动力将横桥放置在肌动蛋白丝附近而参与肌肉收缩的激活。
The l&000-dalton light chain of myosin was phosphorylated and dephosphorylated during the contraction and relaxation cycle of frog muscle. The extent of light chain phosphorylation was a function of stimulus duration in the early phase of contraction. At O” C, 0.14 and 0.22 mol of [S2P] phosphate was transferred/m01 of light chain in muscles which were stimulated for 200 and 500 ms, respectively, and produced 40 and 80% of the maximal tetanic tension, respectively. During a few seconds of tetanization at various temperatures, 0.2 to 0.3 mol of [3eP] phosphate was transferred, whereas electrical stimulation for 20 to 30 s or caffeine treatment for 20 min resulted in esterification of 0.35 to 0.4 mol of [3” P] phosphate. This increase of phosphorylation seems to be related to the continued presence of sarcoplasmic Ca2+ at activating levels, that is,> lO-8 M.Light chain phosphorylation in stimulated semitendinosus muscles stretched beyond the point of overlap of the thick and thin filaments was identical to that in muscles stimulated at standard rest length when the time of stimulation was at least 3 s. The data indicate that the stimulation of the muscle per se and not the mechanical event initiates the phosphorylation. Light chain dephosphorylation took place in the relaxing phase of muscle activity. After short tetani, dephosphorylation approximately followed relaxation. After longer tetani, relaxation occurred before dephosphorylation. In vitro experiments demonstrated that the absence of CaZ+ was required for light chain dephosphorylation and that phosphoryl groups did not turn over during active myofibrillar ATPase. Light chain phosphorylation may be involved in activation of muscle contraction by providing a driving force to place the cross-bridges in the vicinity of actin filaments.