Oxidation of c-Type Cytochromes by the Membrane-Bound Cytochrome Oxidase (Cytochrome aa3) of Blue-Green Algae

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Abstract
Respiratory particles containing an aa3-type cytochrome oxidase were prepared from Anacystis nidulans, Synechocystis 6714, Synechococcus lividus, Anabaena variabilis, Nostoc sp. strain MAC, Nostoc muscorum, and Mastigocladus laminosus. Oxidation of c-type cytochromes by membrane preparations of the different blue-green algae was observed using purified cytochromes from horse heart, Candida krusei, tuna, Saccharomyces oviformis, Rhodospirillum rubrum, Rhodospirillum molischianum, Rhodopseudomonas palustris, Rhodocyclus purpureus, Paracoccus denitrificans, Anacystis nidulans, Anabaena variabilis, Euglena gracilis, and Scenedesmus obliquus. Rapid oxidations were consistently observed with the mitochondrial c-type cytochromes (horse heart cytochrome c reacts most rapidly) and with cytochromes c2 from Rhodopseudomonas palustris and Rhodocyclus purpureus; in contrast, the cytochrome c2 from Rhodospirillum rubrum and the plastidic cytochromes from E. gracilis and Scendesmus obliquus were inactive with all membrane preparations. All reactions were inhibited by low concentrations of KCN, NaN3, and CO, and they were activated by Tween 80, thus indicating participation of the terminal oxidase. The results are discussed in view of the spectral similarities between the terminal oxidase of blue-green algae and the mitochondrial aa3-type cytochrome oxidase of plants and other eukaryotes.