...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Biochemistry >Determination of pK(a) values of carboxyl groups in the N-terminal domain of rat CD2: anomalous pK(a) of a glutamate on the ligand-binding surface.
【24h】

Determination of pK(a) values of carboxyl groups in the N-terminal domain of rat CD2: anomalous pK(a) of a glutamate on the ligand-binding surface.

机译：大鼠CD2 N端结构域中羧基的pK（a）值的测定：配体结合表面上谷氨酸的异常pK（a）。

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The ligand-binding surface of the T-lymphocyte glycoprotein CD2 has an unusually high proportion of charged residues, and ionic interactions are thought to play a significant role in defining the ligand specificity and binding affinity of CD2 with the structurally homologous ligands CD48 (in rodents) and CD58 (in humans). The determination of the electrostatic properties of these proteins can therefore contribute to our understanding of structure-activity relationships for these adhesion complexes that underpin T-cell adhesion to antigen-presenting cells. In this study, we investigated the pH titration behavior of the carboxyl groups of the N-terminal domain of rat CD2 (CD2d1) using the chemical shifts of backbone amide nitrogen-15 ((15)N) and proton NMR resonances, and carboxyl carbon-13 ((13)C) signals. The analysis revealed the presence of a glutamate (Glu41) on the binding surface of rat CD2 with an unusually elevated acidity constant (pK(a) = 6.73) for CD2d1 samples at 1.2 mM concentration. pH titration of CD2d1 at low protein concentration (0.1 mM) resulted in a slight decrease of the measured pK(a) of Glu41 to 6.36. The ionization of Glu41 exhibited reciprocal interactions with a second glutamate (Glu29) in a neighboring location, with both residues demonstrating characteristic biphasic titration behavior of the carboxyl (13)C resonances. Measurements at pH 5.5 of the two-bond deuterium isotope shift for the (13)C carboxyl resonances for Glu41 and Glu29 [(2)DeltaC(delta)(O(epsilon)D) = 0.2 and 0.1 ppm, respectively] were consistent with the assignment of the anomalous pK(a) to Glu41, under the strong influence of Glu29. The characterization of single site mutations of CD2d1 residues Glu41 and Glu29 to glutamine confirmed the anomalous pK(a) for Glu41, and indicated that electrostatic interaction with the Glu29 side chain is a significant contributing influence for this behavior in the wild-type protein. The implications of these observations are discussed with respect to recent structural and functional analyses of the interaction of rat CD2 with CD48. In particular, CD2 Glu41 must be a candidate residue to explain the previously reported strong pH dependence of binding of these two proteins in vitro.
机译：T淋巴细胞糖蛋白CD2的配体结合表面具有异常高的带电残基比例，并且离子相互作用被认为在定义CD2与结构同源配体CD48的配体特异性和结合亲和力中起着重要作用（在啮齿动物中）和CD58（用于人类）。因此，这些蛋白质的静电性质的确定可以有助于我们理解这些粘附复合物的结构-活性关系，这些粘附复合物是T细胞与抗原呈递细胞粘附的基础。在这项研究中，我们使用骨架酰胺氮15（（15）N）和质子NMR共振以及羧基碳原子的化学位移，研究了大鼠CD2（CD2d1）N末端域的羧基的pH滴定行为-13（（13）C）信号。分析显示，在大鼠CD2的结合表面上存在谷氨酸（Glu41），对于浓度为1.2 mM的CD2d1样品，其酸度常数异常升高（pK（a）= 6.73）。低蛋白浓度（0.1 mM）下CD2d1的pH滴定导致Glu41的测得pK（a）略微降低至6.36。 Glu41的电离表现出与邻近位置的第二个谷氨酸（Glu29）的相互作用，两个残基都表现出羧基（13）C共振的特征性双相滴定行为。在pH 5.5下，Glu41和Glu29的（13）C羧基共振的双键氘同位素位移的测量值[（2）DeltaCδ（OεD）分别为0.2和0.1 ppm]与在Glu29的强烈影响下，异常pK（a）分配给Glu41。 CD2d1残基Glu41和Glu29变为谷氨酰胺的单点突变的特征证实了Glu41的异常pK（a），并表明与Glu29侧链的静电相互作用对该野生型蛋白质的这种行为有重要的影响。关于大鼠CD2与CD48相互作用的最新结构和功能分析，讨论了这些观察结果的含义。特别是，CD2 Glu41必须是候选残基，以解释先前报道的这两种蛋白质在体外对结合的强烈pH依赖性。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号