Zhang M, Van Etten R L, Stauffacher C V
Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, USA.
Biochemistry. 1994 Sep 20;33(37):11097-105. doi: 10.1021/bi00203a006.
The first X-ray crystallographic structure of a member of the class of low molecular weight (M(r) 18,000) phosphotyrosyl phosphatases is presented. Bovine heart phosphotyrosyl phosphatase (BHPTP) exemplifies this class and is highly homologous (94% sequence identity) to an isoenzyme known as red cell acid phosphatase that is present throughout human tissues. The high-resolution (2.2-A) crystal structure of BHPTP shows that the enzyme consists of a four-strand central parallel beta sheet with alpha helices packed on both sides in a manner characteristic of a Rossmann fold. A bound phosphate ion defines the active site location in a loop of the first beta alpha beta motif at the C-terminus of the beta sheet. The location and enzymatic significance of the residues in the characteristic low molecular weight PTPase active site motif, including the essential arginine (Arg 18) and nucleophilic cysteine (Cys 12), are described. The functional role of a histidine (His 72) suggested previously to be near the active site is defined in the structure, as well as a potential proton donor for the leaving group in the tyrosyl phosphate cleavage. Surface maps of BHPTP define a hydrophobic crevice suitable for phosphotyrosyl peptide binding. Comparison of the BHPTP structure to the related, but structurally distinct enzyme PTP1B is made, illustrating the unique way this smallest of these phosphatases has formed the phosphotyrosine active site.
本文报道了低分子量（M(r) 18,000）磷酸酪氨酸磷酸酶家族成员的首个X射线晶体学结构。牛心磷酸酪氨酸磷酸酶（BHPTP）是该家族的代表，与一种在人体组织中普遍存在的同功酶——红细胞酸性磷酸酶高度同源（序列同一性为94%）。BHPTP的高分辨率（2.2 Å）晶体结构表明，该酶由一个四链中心平行β折叠组成，α螺旋堆积在两侧，具有Rossmann折叠的特征。一个结合的磷酸根离子确定了β折叠C端第一个β-α-β基序环中的活性位点位置。描述了特征性低分子量PTPase活性位点基序中残基的位置及其酶学意义，包括必需的精氨酸（Arg 18）和亲核半胱氨酸（Cys 12）。结构中确定了先前认为靠近活性位点的组氨酸（His 72）的功能作用，以及磷酸酪氨酸裂解中离去基团的潜在质子供体。BHPTP的表面图谱确定了一个适合磷酸酪氨酸肽结合的疏水裂缝。将BHPTP结构与相关但结构不同的酶PTP1B进行了比较，说明了这种最小的磷酸酶形成磷酸酪氨酸活性位点的独特方式。
