THE ACTIVE-SITE OF METHANOL DEHYDROGENASE CONTAINS A DISULFIDE BRIDGEBETWEEN ADJACENT CYSTEINE RESIDUES

Adjacent cysteine residues can only form disulphide bridges in a disto rted structure containing a cis-peptide link. Such bridges are extreme ly uncommon, identified so far in the acetyl choline receptor alone wh ere the structure of the bridge is undetermined. here we present the f irst molecular description of a disulphide bridge of this type in the quinoprotein methanol dehydrogenase from Methylobacterium extorquens. We show that this structure occurs in close proximity to the pyrrolo-q uinoline quinone prosthetic group and a calcium ion in the active site of the enzyme. This unusual disulphide bridge appears to play a role in the electron transfer reaction mediated by methanol dehydrogenase.