STRUCTURE-FUNCTION-RELATIONSHIPS OF THE ALTERNATIVE OXIDASE OF PLANT-MITOCHONDRIA - A MODEL OF THE ACTIVE-SITE

A major characteristic of plant mitochondria is the presence of a cyan ide-insensitive alternative oxidase which catalyzes the reduction of o xygen to water. Current information on the properties of the oxidase i s reviewed. Conserved amino acid motifs have been identified which sug gest the presence of a hydroxo-bridged di-iron center in the active si te of the alternative oxidase. On the basis of sequence comparison wit h other di-iron center proteins, a structural model for the active sit e of the alternative oxidase has been developed that has strong simila rity to that of methane monoxygenase. Evidence is presented to suggest that the alternative oxidase of plant mitochondria is the newest memb er of the class II group of di-iron center proteins.