Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322-0300, USA.
Arch Biochem Biophys. 2012 Sep 1;525(1):53-9. doi: 10.1016/j.abb.2012.06.002. Epub 2012 Jun 12.
The movement of a conserved protein loop (the WPD-loop) is important in catalysis by protein tyrosine phosphatases (PTPs). Using kinetics, isotope effects, and X-ray crystallography, the different effects arising from mutation of the conserved tryptophan in the WPD-loop were compared in two PTPs, the human PTP1B, and the bacterial YopH from Yersinia. Mutation of the conserved tryptophan in the WPD-loop to phenylalanine has a negligible effect on k(cat) in PTP1B and full loop movement is maintained. In contrast, the corresponding mutation in YopH reduces k(cat) by two orders of magnitude and the WPD loop locks in an intermediate position, disabling general acid catalysis. During loop movement the indole moiety of the WPD-loop tryptophan moves in opposite directions in the two enzymes. Comparisons of mammalian and bacterial PTPs reveal differences in the residues forming the hydrophobic pocket surrounding the conserved tryptophan. Thus, although WPD-loop movement is a conserved feature in PTPs, differences exist in the molecular details, and in the tolerance to mutation, in PTP1B compared to YopH. Despite high structural similarity of the active sites in both WPD-loop open and closed conformations, differences are identified in the molecular details associated with loop movement in PTPs from different organisms.
保守的蛋白质环（WPD 环）的运动在蛋白质酪氨酸磷酸酶（PTP）的催化中很重要。通过动力学、同位素效应和 X 射线晶体学，比较了两种 PTP 中保守色氨酸突变产生的不同影响，即人 PTP1B 和来自耶尔森氏菌的细菌 YopH。将 WPD 环中保守色氨酸突变为苯丙氨酸对 PTP1B 的 k(cat)几乎没有影响，并且完全保持环运动。相比之下，YopH 中的相应突变将 k(cat)降低了两个数量级，并且 WPD 环锁定在中间位置，使广义酸催化失活。在环运动过程中，WPD 环色氨酸的吲哚部分在两种酶中朝相反方向移动。对哺乳动物和细菌 PTP 的比较揭示了围绕保守色氨酸形成的疏水性口袋的残基存在差异。因此，尽管 WPD 环运动是 PTP 中的保守特征，但与 YopH 相比，PTP1B 中存在分子细节和突变耐受性的差异。尽管在 WPD 环打开和关闭构象的活性位点具有高度结构相似性，但在与来自不同生物体的 PTP 中环运动相关的分子细节方面存在差异。
