The binding effect of aptamers on thrombin

Two aptamers that bind separately with exosite I or exosite II of thrombin were studied for better understanding of the binding effect of aptamers on thrombin. CD and intrinsic fluorescence spectra indicated that after binding with aptamers the secondary structure of thrombin seemed unchanged, but the whole conformation of thrombin changed. The binding of aptamers on thrombin also made the catalytic activity of thrombin toward the chromogenic substrate (β-Ala-Gly-Arg-p-nitroanilide diacetate) increased. The present study indicated that the allostery of the two exosites seemed to be independent.