Vikhliantsev I M, Podlubnaia Z A
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia.
Biofizika. 2003 May-Jun;48(3):499-504.
The influence of phosphorylation in vitro of the sarcomere cytoskeletal proteins titin and X-protein of skeletal muscles as well as C-protein of cardiac muscle of ground squirrel Citellus undulatus on the actin-activated ATPase activity of myosin and its Ca2+ sensitivity was studied. It was shown that phosphorylation lowers the activating effect of titin and C-protein and increases the inhibitory effect of X-protein on the enzymatic properties of actomyosin. The phosphorylation of the proteins has the most pronounced influence on Ca2+ sensitivity of actomyosin: it drops to a greater extent in the presence of phosphorylated C-protein and titin and is completely inhibited by phosphorylated X-protein. The inhibitory influence of phosphorylation in vitro of sarcomere cytoskeletal proteins on the above functional properties of the actomyosin system as well as the increase in the extent of phosphorylation of titin in vivo upon hibernation allow one to conclude that this posttranslation modification contributes to adaptive mechanisms of suppression of the contractile ability of muscles in this period.
研究了体外磷酸化草原黄鼠（Citellus undulatus）骨骼肌肌节细胞骨架蛋白肌联蛋白和X蛋白以及心肌C蛋白对肌动蛋白激活的肌球蛋白ATP酶活性及其Ca2+敏感性的影响。结果表明，磷酸化降低了肌联蛋白和C蛋白的激活作用，并增强了X蛋白对肌动球蛋白酶学性质的抑制作用。蛋白质的磷酸化对肌动球蛋白的Ca2+敏感性影响最为显著：在磷酸化的C蛋白和肌联蛋白存在下，Ca2+敏感性下降幅度更大，而磷酸化的X蛋白则完全抑制了Ca2+敏感性。肌节细胞骨架蛋白体外磷酸化对肌动球蛋白系统上述功能特性的抑制作用，以及冬眠期间体内肌联蛋白磷酸化程度的增加，使人们得出结论，这种翻译后修饰有助于这一时期肌肉收缩能力抑制的适应性机制。
