Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, Rhode Island, USA.
Nat Struct Mol Biol. 2010 Apr;17(4):459-64. doi: 10.1038/nsmb.1786. Epub 2010 Mar 21.
The serine/threonine protein phosphatase 1 (PP1) dephosphorylates hundreds of key biological targets. PP1 associates with >or=200 regulatory proteins to form highly specific holoenzymes. These regulatory proteins target PP1 to its point of action within the cell and prime its enzymatic specificity for particular substrates. However, how they direct PP1's specificity is not understood. Here we show that spinophilin, a neuronal PP1 regulator, is entirely unstructured in its unbound form, and it binds PP1 through a folding-upon-binding mechanism in an elongated fashion, blocking one of PP1's three putative substrate binding sites without altering its active site. This mode of binding is sufficient for spinophilin to restrict PP1's activity toward a model substrate in vitro without affecting its ability to dephosphorylate its neuronal substrate, glutamate receptor 1 (GluR1). Thus, our work provides the molecular basis for the ability of spinophilin to dictate PP1 substrate specificity.
丝氨酸/苏氨酸蛋白磷酸酶 1（PP1）去磷酸化数百个关键的生物靶标。PP1 与>200 种调节蛋白结合形成高度特异性的全酶。这些调节蛋白将 PP1 靶向到细胞内的作用点，并为特定底物启动其酶的特异性。然而，它们如何指导 PP1 的特异性尚不清楚。在这里，我们表明，神经元 PP1 调节蛋白 spinophilin 在未结合状态下完全没有结构，它通过结合时折叠的机制以伸展的方式与 PP1 结合，在不改变其活性位点的情况下阻断 PP1 的三个潜在底物结合位点之一。这种结合模式足以使 spinophilin 在体外限制 PP1 对模型底物的活性，而不影响其磷酸化神经元底物谷氨酸受体 1（GluR1）的能力。因此，我们的工作为 spinophilin 决定 PP1 底物特异性的能力提供了分子基础。
