EPHOGSY EXPERIMENTS ON A PARAMAGNETIC PROTEIN - LOCATION OF THE CATALYTIC WATER MOLECULE IN THE HEME CREVICE OF THE OXIDIZED FORM OF HORSE HEART CYTOCHROME-C

The hydration properties of the oxidized form of horse heart cytochrom e c have been studied by H-1 NMR spectroscopy, Application of ePHOGSY (enhanced protein hydration observed through gradient spectroscopy) ex periments over a paramagnetic molecule provided firm spectroscopic evi dence of the presence of a mater molecule in the heme crevice, A few i ntermolecular NOEs have been used to locate the water molecule at abou t 0.65 nm away from the iron atom and to compare the position observed in solution with that observed in the crystal structure and in soluti on for the reduced state, The resulting picture is that there is a det ectable movement of the water molecule upon oxidation, (C) 1997 Federa tion of European Biochemical Societies.