The relationship between effector binding and inhibition of activity in D-3-phosphoglycerate dehydrogenase.
The relationship between effector binding and inhibition of activity in D-3-phosphoglycerate dehydrogenase.
复制标题
D-3-磷酸甘油酸脱氢酶的效应子结合与活性抑制之间的关系。
DOI：
10.1110/ps.8.11.2501
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Hu,Z
中科院分区：
文献类型：
--
作者：
Grant,GA;Xu,XL;Hu,Z
The binding of l-serine to phosphoglycerate dehydrogenase from Escherichia coli displays elements of both positive and negative cooperativity. At pH 7.5, ∼2 mol of serine are bound per mole of tetrameric enzyme. A substantial degree of positive cooperativity is seen for the binding of the second ligand, but the binding of the third and fourth ligand display substantial negative cooperativity. The data indicate a state of ∼50% inhibition when only one serine is bound and ∼80–90% inhibition when two serines are bound. This is consistent with the tethered domain hypothesis that has been presented previously. Comparison of the data derived directly from binding stoichiometry to the binding constants determined from the best fit to the Adair equation, produce a close agreement, and reinforce the general validity of the derived binding constants. The data also support the conclusion that the positive cooperativity between the binding to the first and second site involves binding sites at opposite interfaces over 110 Å apart. Thus, an order of binding can be envisioned where the binding of the first ligand initiates a conformational transition that allows the second ligand to bind with much higher affinity at the opposite interface. This is followed by the third ligand, which binds with lesser affinity to one of the two already occupied interfaces, and in so doing, completes a global conformational transition that produces maximum inhibition of activity and an even lower affinity for the fourth ligand, excluding it completely. Thus, maximal inhibition is accomplished with less than maximal occupancy of effector sites through a mechanism that displays strong elements of both positive and negative cooperativity.
