PDB entries 3wvg, 3wvh, 3wvi, 3wvk and 3wvp

HindIII is a very commonly used restriction endonuclease in molecular biology, recognising the palindromic DNA sequence AACGTT and cleaving between the two adenosine residues. Metal ions are required at the active site for the enzyme to function and previous studies have shown two are present at the active site. It has been unclear however whether one or both ions were needed for catalysis.

Researchers in Japan recently soaked crystals of HindIII and DNA with manganese ions for varying amounts of time and then froze the crystals to investigate the binding rates of the ions and shed light on the reaction mechanism of the enyme. Their work, published in Acta Crystallographica Section D- Biological Crystallography shows the structures of the enzyme soaked in a solution of manganese ions for between zero and 230 seconds. It suggests that HindIII uses a two-metal mechanism to cleave DNA.

The work is descibed by Kawamura et al. in Acta Cryst D. DOI:10.1107/S1399004714025188