EXPRESSION STUDIES ON THE BA(3) QUINOL OXIDASE FROM PARACOCCUS-DENITRIFICANS - A BB(3) VARIANT IS ENZYMATICALLY INACTIVE

Expression of the quinol oxidase from Paracoccus denitrificans has bee n examined using a polyclonal antibody directed against subunit II and a promoter probe vector carrying the promoter region of the qox opero n. Under aerobic conditions nitrate and nitrite act as specific induce rs of the expression. To obtain an enzymatically competent quinol oxid ase complex, an intact ctaB gene is required, which constitutes part o f the cta operon coding for the an, cytochrome c oxidase of P. denitri ficans. Deletion of ctaB leads to a change in heme composition of the quinol oxidase with heme b replacing the high-spin heme a of the binuc lear center, causing loss of electron transport activity.