The high resolution three-dimensional structure of bovine liver rhodanese

The crystal structure of the sulfur complex of bovine liver rhodanese has been determined at a resolution of 2.1 A. The three-dimensional structure of this sulfur-transfer enzyme reveals two domains of roughly equal size, with nearly identical conformations and very dissimilar amino acid sequences. The active site contains four elements which are carefully positioned with respect to each other in order to obtain efficient catalysis: (i) cysteine 247, (ii) a set of peptide nitrogen hydrogen bond donors, (iii) two positively charged residues, and (iv) a cluster of hydrophobic residues at the active site surface. The catalytic mechanism is described in some detail. The structures of the sulfur free enzyme and of the enzyme in complex with several metal cyanide inhibitors have been studied. These inhibitors appear to have one common binding site, blocking the entrance to the active site pocket and thus revealing the mode of inhibition by these, and probably other, anions.