Potts R O, Ford N C, Fournier M J
Biochemistry. 1981 Mar 17;20(6):1653-9. doi: 10.1021/bi00509a038.
The effect of aminoacylation on the structure of yeast phenylalanine tRNA was evaluated by laser light scattering. In these experiments, the translational diffusion coefficient (D20,w) of phenylalanyl-tRNA was monitored continuously during spontaneous deacylation in a variety of solution conditions. The results reveal that significant changes can occur in the hydrodynamic volume and electric charge as a consequence of aminoacylation but that the effects are magnesium dependent. At neutral pH, 20 degrees C, and 0.1 M salt, the D20,w value increased by 18% when deacylation occurred in 2--10 mM Mg2+ concentrations while no change in diffusivity was observed for tRNA deacylating in 0.5--1.0 mM Mg2+. The Mg2+ concentration dependence of the D20,w changes behaves in highly cooperative manner. The electric charges of aminoacyl-tRNA and nonacylated tRNA in 1 and 10 mM Mg2+ were estimated from the diffusive virial coefficients. In the higher Mg2+ conditions, aminoacyl-tRNA has a charge of 15 +/- 2e- while that of the nonacylated form is 10 +/- 2e-; both acylated and nonacylated tRNA have a charge of 11 +/- 4e- in 1 mM Mg2+. Taken together, the results indicate that aminoacylation permits the binding of additional Mg2+, resulting, in turn, in the formation of a more extended conformer of lower diffusivity and greater negative charge. The results also provide a possible explanation for several contradictory results in the literature.
通过激光散射评估了氨酰化对酵母苯丙氨酸tRNA结构的影响。在这些实验中，在各种溶液条件下，对苯丙氨酰 - tRNA的平移扩散系数（D20，w）在自发脱酰化过程中进行了连续监测。结果表明，氨酰化会导致流体动力学体积和电荷发生显著变化，但这些影响取决于镁离子。在中性pH、20℃和0.1M盐的条件下，当在2 - 10mM Mg2+浓度下发生脱酰化时，D20，w值增加了18%，而在0.5 - 1.0mM Mg2+中脱酰化的tRNA未观察到扩散率的变化。D20，w变化对Mg2+浓度的依赖性表现出高度协同的方式。根据扩散维里系数估算了1mM和10mM Mg2+中氨酰 - tRNA和未酰化tRNA的电荷。在较高的Mg2+条件下，氨酰 - tRNA的电荷为15±2e-，而未酰化形式的电荷为10±2e-；在1mM Mg2+中，酰化和未酰化的tRNA电荷均为11±4e-。综合来看，结果表明氨酰化允许额外Mg2+的结合，进而导致形成一种扩散率更低、负电荷更大的更伸展构象。这些结果也为文献中一些相互矛盾的结果提供了一种可能的解释。
