商陆抗病毒蛋白抗核糖体活性的要求。

Requirements for antiribosomal activity of pokeweed antiviral protein.

作者信息

Ready M, Bird S, Rothe G, Robertus J D

出版信息

Biochim Biophys Acta. 1983 May 20;740(1):19-28. doi: 10.1016/0167-4781(83)90116-1.

Abstract

It has been known for some time that pokeweed antiviral protein acts by enzymatically inhibiting protein synthesis on eucaryotic ribosome systems. The site of this action is known to be the ribosome itself. In this paper we show that the pokeweed antiviral protein reaction against ribosomes is a strong function of salt concentrations, where 160 mM K+ and 3 mM Mg2+ retards the reaction, while 20 mM K+ and 2 mM Mg2+ allows maximum reaction rate. It is also shown, however, that an unidentified protein in the postribosomal supernatant solution, together with ATP, allows the ribosome to be attacked even in the presence of high salt. Kinetic analysis of the antiviral protein reaction has been carried out under both sets of conditions, and reveals that the turnover number for the enzyme is about 300-400 mol/mol per min. in each case. The Km for ribosomes is 1 microM in the presence of low salt and 0.2 microM at higher salt in the presence of postribosomal supernatant factors plus ATP. The antiviral protein reaction is also shown to be pH dependent and is controlled by a residue with pKa value of approx. 7.0, apparently a histidine. Stoichiometric reaction of the enzyme with iodoacetamide results in a significant loss of antiribosomal activity.

摘要

一段时间以来，人们已经知道商陆抗病毒蛋白通过酶促抑制真核核糖体系统上的蛋白质合成来发挥作用。已知这种作用的位点是核糖体本身。在本文中，我们表明商陆抗病毒蛋白对核糖体的反应是盐浓度的强函数，其中160 mM K⁺和3 mM Mg²⁺会延缓反应，而20 mM K⁺和2 mM Mg²⁺可使反应速率达到最大值。然而，研究还表明，核糖体后上清液中的一种未知蛋白质与ATP一起，即使在高盐存在的情况下也能使核糖体受到攻击。已在两组条件下对抗病毒蛋白反应进行了动力学分析，结果表明，在每种情况下，该酶的周转数约为每分钟300 - 400摩尔/摩尔。在低盐存在的情况下，核糖体的Km为1微摩尔，在高盐存在且有核糖体后上清液因子加ATP的情况下，Km为0.2微摩尔。抗病毒蛋白反应还显示出对pH的依赖性，并且受pKa值约为7.0的一个残基控制，该残基显然是组氨酸。该酶与碘乙酰胺的化学计量反应会导致抗核糖体活性显著丧失。