TRANSDUCIN INACTIVATION AND ROD LIGHT ADAPTATION

拟议研究的目标是定义新的机制，以规范 视觉感受器中的光传导和适应过程。这个 主要的焦点是确定转导蛋白GTP酶的生理作用 光反应中的调控信使。这项建议是基于 最近发现cGMP磷酸二酯酶，特别是它的伽马- 亚基，可以加速该转导蛋白的GTP酶活性 激活它。CGMP与非催化部位的结合 磷酸二酯酶α和β亚基抑制GTP酶 加速。这表明cGMP不仅仅是一种兴奋的信使。 在光传导中，但也可能调节持续时间 通过反馈机制进行光响应。这样做的第一个目的是 催化cGMP结合位点负责GTP酶的调节和 定义cGMP从这些站点分离的项目规模 导致GTP酶加速。这将表明cGMP是否- 转导蛋白GTP酶的依赖抑制是参与的候选因素 在单一光反应或/和光感受器适应的恢复中 背景照明。第二个目标是使量化 中磷酸二酯酶激活-失活循环的描述 有无cGMP结合到非催化部位。这个 获得的参数将与转导蛋白GTP酶的比率相关 在相同的条件下测量。这种相关性将表明 磷酸二酯酶的关闭是否仅由转导蛋白GTP酶决定 或者涉及到额外的机制。第三个目标是确定 关于加速度的表象。这部分工作的长期目标是 就是通过效应器在不同的G蛋白中寻找活性。这个 建议的实验与理解复杂的反馈有关 调节光感受器活动的控制，可能是 患有几种遗传性视网膜疾病。

The goal of the proposed study is to define new mechanisms regulating the phototransduction and adaptation processes in visual receptors. The major focus is to determine the physiological role of transducin GTPase regulation messenger in the photoresponse. This proposal is based on the recent finding that cGMP phosphodiesterase, specifically its gamma- subunit, can accelerate the GTPase activity of that transducin which activates it. cGMP binding to the non-catalytic sites of phosphodiesterase alpha and beta subunits suppresses the GTPase acceleration. This suggests that cGMP is not only a excitatory messenger in phototransduction but may also regulate the duration of the photoresponse through a feedback mechanism. The first aim of this catalytic cGMP-binding sites are responsible for GTPase regulation and to define the item scale on which cGMP dissociation from these sites causes GTPase acceleration. This will indicate whether the cGMP- dependent suppression of transducin GTPase is a candidate for involvement in recovery rom the single photoresponse or/and photoreceptor adaptation to background illumination. The second aim is to make a quantitative description of the phosphodiesterase activation-inactivation cycle in the presence and absence of cGMP bound to the non-catalytic sites. The obtained parameters will be correlated with the rate of transducin GTPase measured under the same conditions. This correlation will indicate whether phosphodiesterase turnoff is determine only by transducin GTPase or additional mechanisms are involved. The third aim is to determine the epitope on the acceleration. The long-term goal of this part of the work is to look for activity in different G-proteins by their effectors. The experiments proposed are relevant to understanding the intricate feedback controls that regulate photoreceptor activity, controls that may be perturbed in several inherited retinal diseases.