Models for oscillation and bend propagation by flagella.
Models for oscillation and bend propagation by flagella.
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发表时间：
1982
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通讯作者：
C. Brokaw
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作者：
C. Brokaw
模拟包含四态过桥循环的模型鞭毛运动的计算机程序为检验有关产生特定模式的传播弯曲的控制机制的假设提供了有力的工具。正如之前通过更简单的模型所了解到的那样，通过曲率对跨桥活动的简单控制足以产生自发振荡和弯曲传播，但无法再现真实鞭毛行为的许多重要特征。弯曲起始的过程可以通过研究脱膜的海胆精子鞭毛断裂到3-4微米长度的运动，以及研究鞭毛的大部分长度粘在表面时鞭毛的远端运动来分离。为了模拟在这些情况下看到的运动，至少有必要对过桥活动的控制进行一次重大修改。当一个新的弯道形成时，当弯道的曲率达到一个临界值时，交叉桥梁导致弯道形成的主动滑动可以被关闭，正如在早期的模型中一样。然而，相反方向的交叉桥梁的主动滑动，这将导致弯曲的传播，似乎没有同时开启。触发跨桥延迟激活的机制几乎同时贯穿新形成的弯曲的长度尚未确定。据推测，它们与在鞭毛有效行程开始时，在鞭毛的大部分长度上激活滑动的那些相同。
A computer program for simulating the movement of model flagella containing a four-state cross-bridge cycle provides a powerful tool for examining hypotheses about the control mechanisms involved in producing particular patterns of propagated bending. As learned previously with simpler models, a simple control of cross-bridge activity by curvature is sufficient to generate spontaneous oscillation and bend propagation, but fails to reproduce many important features of the behaviour of real flagella. The process of bend initiation can be isolated by studying the movement of demembranated sea urchin sperm flagella broken to lengths of 3-4 microns, and by studying the movement of the distal end of a flagellum when most of the length of the flagellum becomes stuck to a surface. In order to simulate the movement seen in these situations, at least one major modification of the control of cross-bridge activity appears to be necessary. When a new bend is forming, the active sliding of cross-bridges causing the bend to form can be turned off when the curvature of the bend reaches a critical value, as in the earlier models. However, the active sliding of cross-bridges in the opposite direction, which will cause propagation of the bend, does not appear to be turned on at the same time. The mechanisms which trigger this delayed activation of cross-bridges almost simultaneously throughout the length of a newly formed bend have not yet been identified. They are presumably the same as those involved in activating sliding throughout most of the length of a flagellum at the beginning of its effective stroke.