Department of Cell Biology, University of Salzburg, , Hellbrunnerstr. 34, A-5020 Salzburg, Austria.
Proc Biol Sci. 2010 Mar 7;277(1682):803-8. doi: 10.1098/rspb.2009.1618. Epub 2009 Nov 11.
Certain smooth muscles are able to reduce energy consumption greatly when holding without shortening. For instance, this is the case with muscles surrounding blood vessels used for regulating blood flow and pressure. The phenomenon is most conspicuous in 'catch' muscles of molluscs, which have been used as models for investigating this important physiological property of smooth muscle. When the shells of mussels are held closed, the responsible muscles enter the highly energy-efficient state of catch. According to the traditional view, the state of catch is caused by the slowing down of the force-generating cycles of the molecular motors, the myosin heads. Here, we show that catch can still be induced and maintained when the myosin heads are prevented from generating force. This new evidence proves that the long-held explanation of the state of catch being due to the slowing down of force producing myosin head cycles is not valid and that the highly economic holding state is caused by the formation of a rigid network of inter-myofilament connections based on passive molecular structures.
某些平滑肌在不缩短的情况下能够大大降低能量消耗。例如，血管周围用于调节血流量和血压的肌肉就是这种情况。这种现象在软体动物的“捕捉”肌肉中最为明显，这些肌肉被用作研究平滑肌这一重要生理特性的模型。当贻贝的贝壳被紧紧关闭时，负责的肌肉进入高度节能的捕捉状态。根据传统观点，捕捉状态是由产生力的分子马达，肌球蛋白头部的运动速度减慢引起的。在这里，我们表明，即使阻止肌球蛋白头部产生力，也可以诱导和维持捕捉状态。这一新的证据证明，长期以来关于捕捉状态是由于产生力的肌球蛋白头部循环速度减慢的解释是不正确的，而高度经济的保持状态是由基于被动分子结构的肌丝间连接的刚性网络的形成引起的。
