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. Author manuscript; available in PMC: 2007 Oct 15.
Published in final edited form as: Mol Cell. 2007 Feb 23;25(4):531–542. doi: 10.1016/j.molcel.2007.01.015

Table 1.

Transient Kinetics analysis of tRNAHis Variants

tRNA Single Turnover rate of aminoacyl transfer (sec-1) Apparent K1/2 for tRNA in single turnover (μM)* Multiple Turnover rate (sec-1) [32P] AMP burst amplitude, mol AMP/mol active sites Burst phase rate of [32P] AMP formation (sec-1) Linear Turnover Number, [14C]- His-tRNAHis subsat. [ATP] (sec-1) Linear Turnover Number, [32P]-AMP subsat. [ATP] (sec-1)
Wt 18.8 2.5 2.01 No burst No burst 2.31 1.74
G34U 12.5 20 0.37 No burst No burst 0.41 0.67
5’ppp 0.141 12.5 0.195 0.669 0.349 0.0969 0.0869
C73U 0.020 8 0.0063 0.578 7.920 0.00610 0.0134
*

This value is calculated as one half the concentration of tRNA required to obtain a limiting (highest) rate of aminoacyl transfer, which can be assumed to reflect saturation for tRNA binding. The apparent K1/2 is higher than reported Km for wild type tRNAs in steady state kinetics, as the latter value reflects the effect of two tRNA molecules binding to dimeric enzyme during the catalytic cycle, whereas single turnover experiments reflect one tRNA binding to the dimer in the first turnover. All values represent the mean of two to three independent determinations. The standard deviations on these values were typically 5-15%.