Bennett N
Eur J Biochem. 1986 Jun 16;157(3):487-95. doi: 10.1111/j.1432-1033.1986.tb09693.x.
The characterization of a light-induced scattering change in suspensions of rod fragments, which requires previous swelling of the disks by the dark Mg-ATPase described by Uhl et al. [FEBS Lett. 107, 317-322 (1979)] is reported here. Reconstitution experiments demonstrate that this signal is dependent on the presence of G-protein, GTP and cGMP phosphodiesterase. Fast reversal associated with regenerability requires in addition the presence of some protein(s) of the cytoplasm (probably the rhodopsin kinase) and ATP. The amount of excited rhodopsin which saturates the signal is the same as that which saturates the previously described 'dissociation signal' [Kühn et al. (1981) Proc. Natl Acad. Sci. USA 78, 6873-6877] associated with the formation of the phosphodiesterase activator G alpha GTP (alpha subunit of the G-protein with GTP bound). The kinetics of the signal is slightly slower than that of the dissociation signal and its amplitude is proportional to the extent of swelling of the disks. These results suggest that the interaction between G alpha GTP and the phosphodiesterase modifies some structural feature of the disks and provide evidence for the existence of a functional link between the dark Mg-ATPase and the light-induced enzymatic cascade.
本文报道了杆状片段悬浮液中光诱导散射变化的特征，这种变化需要先前由乌尔等人[《欧洲生物化学学会联合会快报》107, 317 - 322 (1979)]所描述的暗态Mg - ATP酶使盘状结构膨胀。重组实验表明，该信号依赖于G蛋白、GTP和cGMP磷酸二酯酶的存在。与可再生性相关的快速逆转还需要细胞质中某些蛋白质（可能是视紫红质激酶）和ATP的存在。使信号饱和的受激发视紫红质的量与使先前描述的与磷酸二酯酶激活剂GαGTP（结合了GTP的G蛋白α亚基）形成相关的“解离信号”[库恩等人(1981)《美国国家科学院院刊》78, 6873 - 6877]饱和的量相同。该信号的动力学比解离信号的动力学稍慢，其幅度与盘状结构的膨胀程度成正比。这些结果表明，GαGTP与磷酸二酯酶之间的相互作用改变了盘状结构的某些结构特征，并为暗态Mg - ATP酶与光诱导酶促级联反应之间存在功能联系提供了证据。
