Copper ions’ influence on thiocyonate dehydrogenase packing and conformation in a crystal

The copper-containing enzyme thiocyanate dehydrogenase (TcDH) catalyzes oxidation of thiocyanate to cyanate and elemental sulfur. To date, the spatial structures of two bacterial TcDHs (tpTcDH and pmTcDH) are known. Both enzymes are dimers and contain a trinuclear copper center in the active site. The important difference between these enzymes is that in a crystal, the subunits of the tpTcDH dimer are in identical conformations, while the subunits of the pmTcDH dimer are in different conformations: closed and open. To clarify the role of copper ions in changing the TcDH conformation, the structure of the apo-form of pmTcDH was established, in which both subunits of the dimer had the closed conformation. Soaking of apo-form crystals with copper led to the restoring of the trinuclear center and the conformational rearrangements of the subunits.