Chloroplast ATP synthase: The clutch between proton flow and ATP synthesis is at the interface of subunit gamma and CF1

Autor(en): Fritsche, O
Junge, W 
Stichwörter: ADENINE-NUCLEOTIDES; ATP synthase; BINDING-SITES; Biochemistry & Molecular Biology; bioenergetics; Biophysics; conformational coupling; COUPLING FACTOR CF1; FACTOR-I; MECHANISM; N-ETHYLMALEIMIDE; OXIDATIVE-PHOSPHORYLATION; PHOTOPHOSPHORYLATION; proton flow; SPINACH-CHLOROPLASTS; THYLAKOID MEMBRANES
Erscheinungsdatum: 1996
Herausgeber: ELSEVIER SCIENCE BV
Journal: BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volumen: 1274
Ausgabe: 3
Startseite: 94
Seitenende: 100
Zusammenfassung: 
ATP synthase, CF0CF1, is both activated and driven by protonmotive force. Composed of more than 20 (8 different) subunits it probably functions as an electro-mechano-chemical transducer. We characterized conformational changes involving subunit gamma of CF1 in response to proton flow through CF0. At the C-terminal end gamma contains one cysteine (Cys(322), `dark site'), which is readily accessible to modification by maleimides. Whereas the modification of this group with a monofunctional maleimide is without effect on the activity, the modification with the bifunctional ortho-phenylenebismaleimide (OPBM), in the presence of protonmotive force, causes a cross-link, induces proton leakage and inhibits photophosphorylation. We used these effects of OPBM to monitor the activity-linked conformational changes involving subunit gamma. These conformational changes were induced by both modes of proton flow through the enzyme, slipping, without added nucleotides, and coupled, at catalytic concentration of ADP causing ATP synthesis. They were not induced when proton flow was blocked at intermediate ADP concentration. The implications are two-fold: (1) Proton slip, i.e., the idling of the proton transport machinery, induces the same type of conformational changes of gamma as the coupled catalytic cycle. (2) The clutch to ATP synthesis resides beyond gamma at its interface with the rest of CF1, i.e., in the F-1-portion of this enzyme.
ISSN: 00052728
DOI: 10.1016/0005-2728(96)00004-7

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