Zhuchenko O P, Semenkov Iu P, Kirillov S V
Mol Biol (Mosk). 1987 Jan-Feb;21(1):266-74.
Experiments on poly(U)-dependent binding of Phe-tRNAPhe to 30S subunits revealed the existence of a critical [Mg2+]/[NH4+] ratio in a medium (approximately 0.05-0.1) with respect to the binding capacity of subunits. If the ratio is greater than the critical one, 30S subunits undergo reversible inactivation even at the highest Mg2+ concentrations (up to 20 mM). The stronger is the deviation from the [Mg2+]/[NH4+] value = 0.05-0.1, the greater are both the rate and extent of such an inactivation. Two sites for tRNA in initially active 30S subunits have been shown to be inactivated in an interdependent way. On the other hand, a progressive decrease of [Mg2+]/[NH4+] ratio in a medium (from the value of 0.05 and lower) does not produce inactivation, but rather results in reduced affinity constants of Phe-tRNAPhe for active sites of 30S subunits.
关于多聚尿苷酸（poly(U)）依赖的苯丙氨酰 - 转移核糖核酸（Phe - tRNAPhe）与30S亚基结合的实验表明，就亚基的结合能力而言，培养基中存在一个关键的镁离子（Mg2+）/铵离子（NH4+）比率（约为0.05 - 0.1）。如果该比率大于临界值，即使在最高镁离子浓度（高达20 mM）下，30S亚基也会发生可逆失活。偏离镁离子/铵离子值 = 0.05 - 0.1的程度越大，这种失活的速率和程度就越大。已表明初始活性的30S亚基中两个转移核糖核酸（tRNA）位点会以相互依赖的方式失活。另一方面，培养基中镁离子/铵离子比率逐渐降低（从0.05及更低的值开始）不会导致失活，而是会导致苯丙氨酰 - 转移核糖核酸对30S亚基活性位点的亲和常数降低。
