Yoshinaka Y, Luftig R B
J Virol. 1981 Mar;37(3):1066-70. doi: 10.1128/JVI.37.3.1066-1070.1981.
Cleavage of murine leukemia virus Pr65gag is associated with the activity of a labile proteolytic factor found in virions. We have shown that the presence of 80 to 100 mM NaCl inhibits this cleavage activity in vitro by over 90%. Further, the addition of 80 to 100 mM excess NaCl in vivo to chronically infected cultures of MJD-54 mouse fibroblasts also caused inhibition of Pr65gag cleavage. Specifically, the excess salt added to cells: (i) caused a greater than 90% decrease in virus production; (ii) increased the Pr65gag/p30 ratio in virions produced by more than threefold; and (iii) in pulse-chase experiments, showed a 10-fold decrease in the amount of Pr65gag cleaved after 3 h. In contrast, during this chase interval there was only a slight diminution, i.e., about two fold, in the cleavage of env precursor polyprotein Pr80env, suggesting that cleavages of Pr65gag and Pr80env are differently controlled. Additionally, electron microscopic examination of the excess salt-treated cells showed a twofold increase in the number of associated immature particles, consistent with the observed higher than average Pr65gag/p30 ratio. The inhibitory effects were also found if excess KCl or MgCl2 was used instead of NaCl, suggesting that they are caused by the hypertonic state of the medium and are not dependent on the ionic species used.
鼠白血病病毒Pr65gag的切割与病毒粒子中一种不稳定的蛋白水解因子的活性相关。我们已经表明，在体外，80至100 mM NaCl的存在可将这种切割活性抑制90%以上。此外，在体内向长期感染的MJD-54小鼠成纤维细胞培养物中添加80至100 mM过量的NaCl也会导致Pr65gag切割受到抑制。具体而言，添加到细胞中的过量盐：(i) 导致病毒产量下降超过90%；(ii) 使产生的病毒粒子中Pr65gag/p30的比例增加了三倍多；(iii) 在脉冲追踪实验中，显示3小时后Pr65gag的切割量下降了10倍。相比之下，在这个追踪间隔期间，env前体多蛋白Pr80env的切割仅略有减少，即约两倍，这表明Pr65gag和Pr80env的切割受到不同的控制。此外，对过量盐处理细胞的电子显微镜检查显示，相关未成熟颗粒的数量增加了两倍，这与观察到的高于平均水平的Pr65gag/p30比例一致。如果使用过量的KCl或MgCl2代替NaCl，也会发现抑制作用，这表明它们是由培养基的高渗状态引起的，而不依赖于所使用的离子种类。
