title: Dicyclohexylcarbodiimide inhibits proton pumping in ubiquinol:cytochrome c oxidoreductase of Rhodobacter sphaeroides and binds to aspartate-187 of cytochrome b.
abstract: In recent studies we reported that dicyclohexylcarbodiimide (DCCD) inhibited proton translocation in ubiquinol:cytochrome c oxidoreductase (cytochrome bc1 complex) from yeast mitochondria where it was bound to aspartate-160 of cytochrome b. In the current study, we report that DCCD and its fluorescent analogue, N-cyclohexyl-N'-[4-(dimethylamino)naphthyl]-carbodiimide (NCD-4), inhibit 50-60% proton pumping in the cytochrome bc1 complex of the bacterium Rhodobacter sphaeroides with a 20% inhibition of electron transfer activity. Radioactive DCCD is bound exclusively to cytochrome b at aspartate-187, which is located at the C-terminal region of the CD loop connecting membrane-spanning helices C and D of cytochrome b. Fluorescent studies with NCD-4 revealed that aspartate-187 is located in a mildly hydrophobic pocket in the bc1 complex at a distance of 2-3 A from the surface of the membrane.
authors.affiliation: Department of Biochemistry, West Virginia University School of Medicine, Morgantown 26505-9142, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Wang
authors.forename: V
authors.initials: V
authors.lastname: Obungu
authors.forename: D S
authors.initials: DS
authors.lastname: Beattie
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D002234:Carbodiimides / Q000494:pharmacology; D003573:Cytochrome b Group / Q000737:chemistry*; D004024:Dicyclohexylcarbodiimide / Q000031:analogs & derivatives / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors*; D005456:Fluorescent Dyes / Q000378:metabolism; D011485:Protein Binding; D054328:Proton Pump Inhibitors; D011522:Protons; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D013050:Spectrometry, Fluorescence; D014357:Trypsin / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002234:Carbodiimides; D003573:Cytochrome b Group; D005456:Fluorescent Dyes; D054328:Proton Pump Inhibitors; D011522:Protons; D004024:Dicyclohexylcarbodiimide; C038088:N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide; D014357:Trypsin; D014450:Electron Transport Complex III