Abstract: Alternative oxidase (AOX), a terminal oxidase located in the inner mitochondrial membrane , has been identified universally in plant , algae , fungi, and protozoan . AOX branches from the cytochrome pathway at the level of the ubiquinone and catalyses the oxidation of ubiquinol and reduction of oxygen to water . There is non-protonmotive and energy is liberated as heat instead of producing ATP . In thermogenic plants, heat released by AOX attracts insects for pollination by heating aromatic compounds . The use of AOX in plant may ( a) allow flexibility of respiration under changing environmental conditions (b) regulate energy homeostasis ( c ) help prevent oxidative stress ( d ) maintain TCA cycle turnover. AOX is a member of di- iron carboxylate proteins . Two structural models exist for AOX and the latest one is a monotopic protein instead of span membrane . Relatively little is known about its 3-dimensional structure. Main reason is that the sufficient quantities of AOX suitable for crystallogram structural studies is unavailable because of its unstableness . Recently we tried to obtain sufficient quantities alternative oxidase protein (AOX) for further construction studies . The aim is achieved
by over-expressing in E. coli and improving purification of native AOX from Arum mitochondrial .

Key words: Alternative Oxidase