National Center for
5EPZ: Human Angiogenin in complex with sulphate anions at a basic solution
FEBS Lett. (2016) 590 p.3005-3018
In this study, we investigate the inhibition of human angiogenin by ammonium sulfate. The inhibitory potency of ammonium sulfate for human angiogenin (IC50 = 123.5 +/- 14.9 mm) is comparable to that previously reported for RNase A (119.0 +/- 6.5 mm) and RNase 2 (95.7 +/- 9.3 mm). However, analysis of two X-ray crystal structures of human angiogenin in complex with sulfate anions (in acidic and basic pH environments, respectively) indicates an entirely distinct mechanism of inhibition. While ammonium sulfate inhibits the ribonucleolytic activity of RNase A and RNase 2 by binding to the active site of these enzymes, sulfate anions bind only to peripheral substrate anion-binding subsites of human angiogenin, and not to the active site.