Hi Kumar,
I suggest to try Fe in the active site since it binds with Asp and His which is typical binding motif of Fe. Best, Ping At 2015-07-09 17:35:10, "Dilip Kumar" <[email protected]> wrote: Dear All I have solved a structure of a metal-ion dependent exonuclease enzyme. In homologous structures, two or three Manganese ions are present at catalytic center. However, I have used 2 mM MgCl2 in protein purification buffer. I tried to fit both of these metal ions at catalytic center but in both cases it still shows green density (Sigma level ~ 7) in difference map and low b-factor (<10) for these metal ions. For better understanding I have attached the screenshot of metal ions with difference map on. Please suggest me the possible reasons or methods to validate the presence of any other metal ions at catalytic center. Thanks in advance. Regards Dilip Kumar Research Associate Chemical and Systems Biology Unit CSIR-Institute of Genomics & Integrative Biology Delhi-110025
