Kinetics of turn-offs of frog rod phototransduction cascade.
Kinetics of turn-offs of frog rod phototransduction cascade.
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DOI：
10.1085/jgp.200810034
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发表时间：
2008-11
期刊：
影响因子：
--
通讯作者：
Govardovskii VI
中科院分区：
文献类型：
--
作者：
Astakhova LA;Firsov ML;Govardovskii VI
视紫红质和转导素关闭的动力学决定了光诱导的光合作用效应酶cGMP-磷酸二酯酶（PDE）活性的时间进程。这两个过程是决定光反应速度和灵敏度的关键因素，其调节有助于光适应。本研究的目的是确定时间过程中的闪光灯引起的PDE活动在青蛙杆暗适应或受到非饱和稳定的背景照明。PDE活性计算的反应记录从孤立杆与吸移管技术在Ca 2 +-钳制溶液。在暗适应状态下施加的闪光激发PDE活动的波，其上升和衰减阶段的特征时间分别接近0.5秒和2秒。非饱和稳定背景使两个相位缩短的程度大致相同。在抑制暗电流约70%的背景下，加速可超过5倍。控制从超饱和闪光恢复的过程的时间常数（所谓的主导时间常数）与适应无关，因此不能归因于塑造偏微分方程波主要部分的任何过程。我们假设，青蛙杆中的主导时间常数表征arrestin结合到视紫红质部分失活的磷酸化。级联的数学模型，认为两个阶段的视紫红质淬灭和transformin失活可以很好地模拟实验PDE活性。光适应对PDE动力学的影响可以在模型中通过同时加速视紫红质磷酸化和转导蛋白关闭来再现，但不能通过加速抑制蛋白结合来再现。这表明不仅视紫红质，而且转导蛋白关闭也在适应控制下。
The time course of the light-induced activity of phototrandsuction effector enzyme cGMP-phosphodiesterase (PDE) is shaped by kinetics of rhodopsin and transducin shut-offs. The two processes are among the key factors that set the speed and sensitivity of the photoresponse and whose regulation contributes to light adaptation. The aim of this study was to determine time courses of flash-induced PDE activity in frog rods that were dark adapted or subjected to nonsaturating steady background illumination. PDE activity was computed from the responses recorded from solitary rods with the suction pipette technique in Ca2+-clamping solution. A flash applied in the dark-adapted state elicits a wave of PDE activity whose rising and decaying phases have characteristic times near 0.5 and 2 seconds, respectively. Nonsaturating steady background shortens both phases roughly to the same extent. The acceleration may exceed fivefold at the backgrounds that suppress ≈70% of the dark current. The time constant of the process that controls the recovery from super-saturating flashes (so-called dominant time constant) is adaptation independent and, hence, cannot be attributed to either of the processes that shape the main part of the PDE wave. We hypothesize that the dominant time constant in frog rods characterizes arrestin binding to rhodopsin partially inactivated by phosphorylation. A mathematical model of the cascade that considers two-stage rhodopsin quenching and transducin inactivation can mimic experimental PDE activity quite well. The effect of light adaptation on the PDE kinetics can be reproduced in the model by concomitant acceleration on both rhodopsin phosphorylation and transducin turn-off, but not by accelerated arrestin binding. This suggests that not only rhodopsin but also transducin shut-off is under adaptation control.
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通过其靶酶和CGMP对光感受器G蛋白的失活调节。
影响因子：
64.8
作者：
Arshavsky VYu;Bownds MD
通讯作者：
Bownds MD
DOI：
10.1085/jgp.200308832
发表时间：
2003-10
期刊：
The Journal of general physiology
影响因子：
--
作者：
Hamer RD;Nicholas SC;Tranchina D;Liebman PA;Lamb TD
通讯作者：
Lamb TD
影响因子：
3.8
作者：
COBBS, WH
通讯作者：
COBBS, WH
影响因子：
16.2
作者：
ANGLESON, JK;WENSEL, TG
通讯作者：
WENSEL, TG
影响因子：
3.5
作者：
GORODOVIKOVA, EN;GIMELBRANT, AA;PHILIPPOV, PP
通讯作者：
PHILIPPOV, PP