The inhibitory γ subunit of the rod cGMP phosphodiesterase binds the catalytic subunits in an extended linear structure
The inhibitory γ subunit of the rod cGMP phosphodiesterase binds the catalytic subunits in an extended linear structure
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DOI：
10.1074/jbc.m600595200
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发表时间：
2006-06-02
影响因子：
4.8
通讯作者：
Ruoho, Arnold E.
中科院分区：
文献类型：
--
作者：
Guo, Lian-Wang;Muradov, Hakim;Ruoho, Arnold E.
视杆细胞cGMP磷酸二酯酶（PDE 6）的独特特征是存在抑制性亚基（P γ），其与催化性异源二聚体（P α β）相互作用以调节其活性。这种独特性导致视杆细胞视觉信号的极高灵敏度和复杂调制，其中P γ/P α β相互作用起关键作用。四元组织的α-β-γ-γ异四聚体是知之甚少，相互作用的相互矛盾的模式已经提出。在这里，我们提供的证据，支持一个特定的相互作用，通过系统和差异分析的P α和P β通过光标记从整个分子的各个P γ位置转移的P γ-结合区域。发现P γ N-末端瓦尔（16）-Phe（30）区与P α β GAFa结构域相互作用，而其C-末端（Phe（73）-Ile（87））与P α β催化结构域相互作用. P γ与这两个结构域的相互作用通过其中心Ser（40）-Phe（50）区域通过与GAFb的相互作用以及GAFb与催化结构域之间的接头桥接，表明P α和P α β之间的线性和扩展的相互作用。此外，光交联产物α β γ（γ）是由双衍生的P γ，其中一个光探针位于聚阳离子区域和其他在C末端特异性地产生。综上所述，证据支持以下结论：每个P γ分子以扩展的线性相互作用结合P α β，甚至可能同时与P α和P β相互作用。
The unique feature of rod photoreceptor cGMP phosphodiesterase (PDE6) is the presence of inhibitory subunits (P gamma), which interact with the catalytic heterodimer (P alpha beta) to regulate its activity. This uniqueness results in an extremely high sensitivity and sophisticated modulations of rod visual signaling where the P gamma/P alpha beta interactions play a critical role. The quaternary organization of the alpha beta gamma gamma heterotetramer is poorly understood and contradictory patterns of interaction have been previously suggested. Here we provide evidence that supports a specific interaction, by systematically and differentially analyzing the P gamma-binding regions on P alpha and P beta through photolabel transfer from various P gamma positions throughout the entire molecule. The P gamma N- terminal Val(16)-Phe(30) region was found to interact with the P alpha beta GAFa domain, whereas its C terminus (Phe(73)-Ile(87)) interacted with the P alpha beta catalytic domain. The interactions of P gamma with these two domains were bridged by its central Ser(40)-Phe(50) region through interactions with GAFb and the linker between GAFb and the catalytic domain, indicating a linear and extended interaction between P alpha and P alpha beta. Furthermore, a photocross-linked product alpha beta gamma(gamma) was specifically generated by the double derivatized P gamma, in which one photoprobe was located in the polycationic region and the other in the C terminus. Taken together the evidence supports the conclusion that each P gamma molecule binds P alpha beta in an extended linear interaction and may even interact with both P alpha and P beta simultaneously.