Rath V L, Fletterick R J
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA.
Nat Struct Biol. 1994 Oct;1(10):681-90. doi: 10.1038/nsb1094-681.
The structure of the unphosphorylated, inactive form of yeast glycogen phosphorylase has been determined to a resolution of 2.6 A. The structure is similar to the phosphorylated, active form of muscle phosphorylase in the orientations of the subunits and catalytic residues, but resembles the inactive muscle enzyme in the closed, or substrate excluding, orientation of the two domains. Part of the unique yeast amino-terminal extension of 40 residues binds near the catalytic site of the second subunit in the homodimer, preventing the domain movement required for substrate access. Phosphorylation may displace the amino terminus from the active site, allowing the domains to separate.
已确定酵母糖原磷酸化酶未磷酸化的无活性形式的结构，分辨率达到2.6埃。在亚基和催化残基的取向上，该结构与肌肉磷酸化酶的磷酸化活性形式相似，但在两个结构域的封闭（即排除底物）取向上类似于无活性的肌肉酶。在同型二聚体中，酵母特有的40个残基的氨基末端延伸部分的一部分结合在第二个亚基的催化位点附近，阻止了底物进入所需的结构域移动。磷酸化可能会将氨基末端从活性位点上置换下来，使结构域分离。
