Iwata S, Kamata K, Yoshida S, Minowa T, Ohta T
Department of Agricultural Chemistry, University of Tokyo, Japan.
Nat Struct Biol. 1994 Mar;1(3):176-85. doi: 10.1038/nsb0394-176.
The crystal structure of L-lactate dehydrogenase from Bifidobacterium longum, determined to 2.5 A resolution, contains a regular 1:1 complex of T- and R-state tetramers. A comparison of these two structures within the same crystal lattice and kinetical characterization of the T-R transition in solution provide an explanation for the molecular mechanism of allosteric activation. Substrate affinity is controlled by helix sliding between subunits which is triggered by the binding of the activator, fructose 1,6-bisphosphate. The proposed mechanism can explain activation by chemical modification and mutagenesis, as well as suggesting why vertebrate counterparts are not allosteric.
长双歧杆菌L-乳酸脱氢酶的晶体结构，分辨率为2.5埃，包含T态和R态四聚体的规则1:1复合物。在同一晶格内对这两种结构进行比较，并对溶液中T-R转变进行动力学表征，为别构激活的分子机制提供了解释。底物亲和力由亚基间的螺旋滑动控制，而螺旋滑动由激活剂1,6-二磷酸果糖的结合触发。所提出的机制可以解释化学修饰和诱变引起的激活，也能说明为什么脊椎动物的对应物不是别构的。
