Wagner R, Ryba N, Uhl R
Max-Planck-Institut für Biophysikalische Chemie, Göttingen, FRG.
FEBS Lett. 1989 Jan 2;242(2):249-54. doi: 10.1016/0014-5793(89)80479-x.
The kinetics of the light-induced activation of transducin as well as the subsequent disactivation process can be monitored by means of a specific light scattering transient PA. In this communication it is demonstrated that the rate of transducin disactivation is calcium dependent, increasing when the calcium concentration is decreased. As a consequence of the accelerated recovery in low calcium, the time to the peak of the transducin activation process is shortened and the gain of the primary amplification step, i.e. the number of transducin molecules activated per bleached rhodopsin, is reduced. Experiments using hydroxylamine as an artificial quencher of rhodopsin activity suggest that calcium acts upon rhodopsin kinase and not upon the rate of the GTPase. This would indicate that calcium may control visual adaptation not only by regulating guanine cyclase activity, but also by affecting the primary step in the transduction cascade, the rhodopsin-transducin coupling.
转导素光诱导激活的动力学以及随后的失活过程可以通过特定的光散射瞬态PA进行监测。在本通讯中表明，转导素失活速率依赖于钙，当钙浓度降低时增加。由于在低钙条件下恢复加速，转导素激活过程达到峰值的时间缩短，并且初级放大步骤的增益，即每个漂白视紫红质激活的转导素分子数量减少。使用羟胺作为视紫红质活性的人工猝灭剂的实验表明，钙作用于视紫红质激酶而不是GTPase的速率。这表明钙可能不仅通过调节鸟苷酸环化酶活性，还通过影响转导级联反应的初级步骤，即视紫红质 - 转导素偶联来控制视觉适应。
