title: Primary structure of a novel subunit in ba3-cytochrome oxidase from Thermus thermophilus.
abstract: The bax-type cytochrome c oxidase from Thermus thermophilus is known as a two subunit enzyme. Deduced from the crystal structure of this enzyme, we discovered the presence of an additional transmembrane helix "subunit IIa" spanning the membrane. The hydrophobic N-terminally blocked protein was isolated in high yield using high-performance liquid chromatography. Its complete amino acid sequence was determined by a combination of automated Edman degradation of both the deformylated and the cyanogen bromide cleaved protein and automated C-terminal sequencing of the native protein. The molecular mass of 3,794 Da as determined by MALDI-MS and by ESI requires the N-terminal methionine to be formylated and is in good agreement with the value calculated from the formylmethionine containing sequence (3,766.5 Da + 28 Da = 3,794.5 Da). This subunit consits of 34 residues forming one helix across the membrane (Lys5-Ala34), which corresponds in space to the first transmembrane helix of subunit II of the cytochrome c oxidases from Paracoccus denitrificans and bovine heart, however, with opposite polarity. It is 35% identical to subunit IV of the ba3-cytochrome oxidase from Natronobacterium pharaonis. The open reading frame encoding this new subunit IIa (cbaD) is located upstream of cbaB in the same operon as the genes for subunit I (cbaA) and subunit II (cbaB).
authors.affiliation: Rheinisch-Westfälische Technische Hochschule Aachen, Institut für Biochemie, Germany. tsoulimane@post.klinikum.rwth-aachen.de
authors.forename: T
authors.initials: T
authors.lastname: Soulimane
authors.forename: M E
authors.initials: ME
authors.lastname: Than
authors.forename: M
authors.initials: M
authors.lastname: Dewor
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: G
authors.initials: G
authors.lastname: Buse
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D002851:Chromatography, High Pressure Liquid; D003488:Cyanogen Bromide / Q000378:metabolism; D003573:Cytochrome b Group / Q000737:chemistry*; D003576:Electron Transport Complex IV / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D008715:Methionine / Q000737:chemistry; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009206:Myocardium / Q000201:enzymology; D016366:Open Reading Frames; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D021241:Spectrometry, Mass, Electrospray Ionization; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D016963:Thermus thermophilus / Q000737:chemistry*
chemical_list: D003573:Cytochrome b Group; D008715:Methionine; C058557:cytochrome ba3; D003576:Electron Transport Complex IV; D003488:Cyanogen Bromide