Kinetics of denaturation of the yellow fluorescent protein from coral zFP538

摘要

Our experiments show that fluorescence dependence of zFP538 on protein concentration is nonlinear over therange from 1.2·10~(-9) М to 5.5·10~(-7) М. Under pH from 5 to 9 it can be divided into two linear regions with different slopeat concentration more and less than 1·10~(-7) М. One may conclude, there are at least two different forms of the yellowprotein observed in the high (>1·10~(-7) М) and low (<1·10~(-7) М) concentration regions. These forms may be differentaggregation states of the protein. We have obtained acid denaturation kinetics curves for zFP538 over pH range from 3.5to 5.5 at different protein concentrations. Under all pH values relative residual fluorescence of the most concentratedsolution (1.33·10~(-6) М) is higher than that for the solutions of lower protein concentration (1.36·10~(-7) М and 1.36·10~(-8) М).Fluorescence decrease under pH from 3.5 to 4.24 is three or two exponential. Under higher pH values kinetic curveshave a plateau at first and then fluorescence drops in exponential way. The results obtained support the hypothesis that athigher protein concentrations zFP538 is more stable against acid denaturation.