Neutron crystallography for the understanding of enzymatic mechanisms

By using neutron crystallography, we determined the precise three-dimensional structure of a copper-containing nitrite reductase (CuNIR), a protein enzyme involved in the nitrogen cycle. Our data visualizes the positions of hydrogen atoms at the catalytic site and a hydroxide-bound state of CuNIR, which has been proposed by quantum chemical calculations. Other experimental findings including a tight hydrogen bond on a possible electron transfer pathway also supports previous results from theoretical chemistry. (author)