the elusive third subunit iia of the bacterial b-type oxidases the enzyme from the hyperthermophile aquifex aeolicus难以捉摸的第三单元活动花絮的细菌b型氧化酶类酶超嗜热菌aquifex aeolicus.pdf

The Elusive Third Subunit IIa of the Bacterial B-Type Oxidases: The Enzyme from the Hyperthermophile Aquifex aeolicus 1 1,2 ´ 3 ´ ` 1 Laurence Prunetti , Myriam Brugna , Regine Lebrun , Marie-Therese Giudici-Orticoni , Marianne Guiral1* ´ ´ ´ ´ ´ ´ 1 Laboratoire de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee (IFR88)-Centre National de la Recherche Scientifique, ´ ´ ´ Marseille, France, 2 Universite de Provence, Marseille, France, 3 Plate-forme Proteomique de l’IFR88-Centre National de la Recherche Scientifique, Marseille Proteomique, Marseille, France Abstract The reduction of molecular oxygen to water is catalyzed by complicated membrane-bound metallo-enzymes containing variable numbers of subunits, called cytochrome c oxidases or quinol oxidases. We previously described the cytochrome c oxidase II from the hyperthermophilic bacterium Aquifex aeolicus as a ba3-type two-subunit (subunits I and II) enzyme and showed that it is included in a supercomplex involved in the sulfide-oxygen respiration pathway. It belongs to the B-family of the heme-copper oxidases, enzymes that are far less studied than the ones from family A. Here, we describe the presence in this enzyme of an additional transmembrane helix ‘‘subunit IIa’’, which is composed of 41 amino acid residues with a measured molecular mass of 5105 Da. Moreover, we show that subunit II, as expected, is in fact longer than the originally annotated protein (from the genome) an