Skip to main content
. Author manuscript; available in PMC: 2009 Feb 1.
Published in final edited form as: Methods. 2008 Feb;44(2):100–118. doi: 10.1016/j.ymeth.2007.09.007

Figure 2.

Figure 2

Active site titration to determine the concentration of HisRS. The disappearance of ATP is fit to an equation that is based on a first order exponential decay followed by a linear phase. The concentration of active enzyme is determined from the burst amplitude. The two plots shown represent two different concentrations of histidyl-tRNA synthetase, with the top plot representing a reaction performed using 2 μM HisRS, and the lower plot representing HisRS at 4 μM. Note that the steady state rate of ATP consumption in both cases is the same: the key difference is in the amplitude of the exponential.