Eccleston J F, Dix D B, Thompson R C
J Biol Chem. 1985 Dec 25;260(30):16237-41.
Interaction of Phe-tRNA.elongation factor Tu.GTP with poly(U)-programmed ribosomes containing an occupied P site can be described by a three-step kinetic mechanism. Initial binding is followed by the cleavage of GTP, and then a new peptide bond is formed. Rate constants controlling the first and third of these reactions are known, but only a lower limit for the rate constant of the cleavage step has been reported. We have determined this rate constant to be 20 s-1 at 5 degrees C, 30 s-1 at 15 degrees C, and 50 s-1 at 25 degrees C. This is much faster than the reverse step of the initial binding process and implies that the intrinsic accuracy of the ribosome in the initial selection step is sacrificed in favor of speed. The similarity of the kinetic and chemical mechanism of this GTP cleavage step with other nucleoside 5'-triphosphatases is discussed.
苯丙氨酰 - 转移核糖核酸（Phe - tRNA）、延伸因子Tu、鸟苷三磷酸（GTP）与含有被占据P位点的聚尿苷酸（poly(U)）编程核糖体之间的相互作用可用三步动力学机制来描述。首先是初始结合，随后是GTP的裂解，然后形成一个新的肽键。控制这些反应第一步和第三步的速率常数是已知的，但关于裂解步骤速率常数仅报道了一个下限。我们已确定该速率常数在5℃时为20 s⁻¹，15℃时为30 s⁻¹，25℃时为50 s⁻¹。这比初始结合过程的逆向步骤快得多，这意味着核糖体在初始选择步骤中的内在准确性为了速度而被牺牲。本文还讨论了该GTP裂解步骤与其他核苷5'-三磷酸酶在动力学和化学机制上的相似性。
