Regulation of voltage-dependent K+ channels by methionine oxidation: effect of nitric oxide and vitamin C

Methionine oxidation is known to alter functional properties of a transient A-type potassium channel expressed in Xenopus oocytes. We show here that n itric oxide (NO) slows down the K+ channel inactivation time course by oxid izing a critical methionine residue in the inactivation hall domain of the channel protein. We also demonstrate that the channel protein is protected from methionine oxidation by the enzyme methionine sulfoxide reductase and the antioxidant vitamin C, (C) 1999 Federation of European Biochemical Soci eties.