Molecular analysis of the cytochrome bc(1)-aa(3) branch of the Corynebacterium glutamicum respiratory chain containing an unusual diheme cytochrome c(1)

Niebisch, A Bott, M

A. Niebisch et M. Bott, Molecular analysis of the cytochrome bc(1)-aa(3) branch of the Corynebacterium glutamicum respiratory chain containing an unusual diheme cytochrome c(1), ARCH MICROB, 175(4), 2001, pp. 282-294

56

INGLESE

Article

Microbiology

ARCHIVES OF MICROBIOLOGY

0302-8933 → ACNP

175

4

2001

282 - 294

ISI

0302-8933(200104)175:4<282:MAOTCB>2.0.ZU;2-X

In this work, the genes for cytochrome aa(3) oxidase and the cytochrome bc( 1) complex in the gram-positive soil bacterium Corynebacterium glutamicum w ere identified. The monocistronic ctaD gene encoded a 65-kDa protein with a ll features typical for subunit I of cytochrome aa: oxidases. A ctaD deleti on mutant lacked the characteristic 600 nm peak in redox difference spectra . and growth in glucose minimal medium was strongly impaired. The genes enc oding subunit III of cytochrome aa3 ctaE) and the three characteristic subu nits of the cytochrome bc(1), complex (qcrABC) were clustered in the order ctaE-qcrCAB. Analysis of the deduced primary structures revealed a number o f unusual features: (1) cytochrome c(1) (QcrC, 30 kDa) contained two Cys-X- X-Cys-His motifs for covalent heme attachment, indicating that it is a dihe me c-type cytochrome: (2) the 'Rieske' iron-sulphur protein (QcrA, 45 kDa) contained three putative transmembrane helices in the N-terminal region rat her than only one; and (3) cytochrome b (QcrB, 60 kDa) contained, in additi on to the conserved part with eight trans membrane helices, a C-terminal ex tension of about 120 amino acids, which presumably is located in the cytopl asm. Staining of C. glutamicum proteins for covalently bound heme indicated the presence of a single, membrane-bound c-type cytochrome with an apparen t molecular mass of about 31 kDa. Since this protein was missing in a qcrCA B deletion mutant, it most likely corresponds to cytochrome c(1). Similar t o the Delta ctaD mutant, the Delta qcrCAB mutant showed strongly impaired g rowth in glucose minimal medium. which indicates that the bc(1)-aa(3) pathw ay is the main route of respiration under these conditions.