Influence of ionic strength on contractile force and energy consumption of skinned fibers from mammalian and crustacean striated muscle.
Influence of ionic strength on contractile force and energy consumption of skinned fibers from mammalian and crustacean striated muscle.
复制标题
离子强度对哺乳动物和甲壳类横纹肌皮纤维的收缩力和能量消耗的影响。
DOI：
10.1007/978-1-4615-2872-2_67
复制
发表时间：
1993
影响因子：
--
通讯作者：
Nosek,TM
中科院分区：
文献类型：
--
作者：
Godt,RE;Fogaça,RT;Andrews,MA;Nosek,TM
增加离子强度通过不完全理解的机制降低皮肤肌纤维的最大钙激活力（Fmax）。在来自兔子（腰肌）或龙虾（腿或腹部）的洗涤剂皮肤纤维中，含Fmaxin KCl的溶液低于甲磺酸钾（KMeSO 3），我们以前表明这是调节离子强度的最有害的盐。在任一盐中，龙虾纤维对离子强度升高的敏感性大大低于兔纤维。三甲胺N-氧化物（TMAO，在耐盐动物的细胞中以高浓度发现的两性离子渗透剂）增加Fmax，特别是在高KCl溶液中。在这方面，TMAO比各种其他天然或合成的两性离子更有效。在兔纤维中，增加离子强度降低Fmax，但对同时使用连接酶测定法测量的收缩ATP酶速率几乎没有影响。因此，高盐增加了收缩的张力-成本（即ATP酶/Fmax的比率）。在高盐和低盐条件下，TMAO均降低了张力成本。给出一个简单的两态模型的跨桥周期，这些数据表明，离子强度和TMAO影响的表观脱离速率常数。高离子强度KCl溶液从兔纤维中提取肌球蛋白重链和轻链以及肌钙蛋白C。这种提取实际上被TMAO废除了。天然两性离子，如TMAO，已被证明可以保护蛋白质免受高盐或其他变性剂的不稳定性。我们的数据表明，即使在最好的盐，不稳定的肌动球蛋白复合物可能发挥作用的影响，高离子强度的收缩过程。
Increased ionic strength decreases maximal calcium-activated force (Fmax) of skinned muscle fibers via mechanisms that are incompletely understood. In detergent-skinned fibers from either rabbit (psoas) or lobster (leg or abdomen), Fmaxin KCl-containing solutions was less than in potassium methanesulfonate (KMeSO3), which we showed previously was the least deleterious salt for adjusting ionic strength. In either salt, lobster fibers were considerably less sensitive to elevated ionic strength than rabbit fibers. Trimethylamine N-oxide (TMAO, a zwitterionic osmolyte found in high concentration in cells of salt-tolerant animals) increased Fmax, especially in high KC1 solutions. In this regard, TMAO was more effective than a variety of other natural or synthetic zwitterions. In rabbit fibers, increasing ionic strength decreases Fmaxbut has little effect on contractile ATPase rate measured simultaneously using a linked-enzyme assay. Thus high salt increases the tension-cost of contraction (i.e. ratio ATPase/Fmax). At both high and low salt, TMAO decreases tension-cost. Given a simple two-state model of the cross-bridge cycle, these data indicate that ionic strength and TMAO affect the apparent detachment rate constant. High ionic strength KC1 solutions extract myosin heavy and light-chains, and troponin C from rabbit fibers. This extraction is virtually abolished by TMAO. Natural zwitterions, such as TMAO, have been shown to protect proteins against destabilization by high salt or other denaturatants. Our data indicate that, even in the best of salts, destabilization of the actomyosin complex may play a role in the effect of high ionic strength on the contractile process.