Asymmetric binding of stigmatellin to the dimeric Paracoccus denitrificans bc1 complex: evidence for anti-cooperative ubiquinol oxidation and communication between center P ubiquinol oxidation sites.

Content Provider	Semantic Scholar
Author	Covián, Raúl Kleinschroth, Thomas
Copyright Year	2007
Abstract	We have investigated the mechanism responsible for half-of-the-sites activity in the dimeric cytochrome bc(1) complex from Paracoccus denitrificans by characterizing the kinetics of inhibitor binding to the ubiquinol oxidation site at center P. Both myxothiazol and stigmatellin induced a 2-3 nm shift of the visible absorbance spectrum of the b(L) heme. The shift generated by myxothiazol was symmetric, with monophasic kinetics that indicate equal binding of this inhibitor to both center P sites. In contrast, stigmatellin generated an asymmetric shift in the b(L) spectrum, with biphasic kinetics in which each phase contributed approximately half of the total magnitude of the spectral change. The faster binding phase corresponded to a more symmetrical shift of the b(L) spectrum relative to the slower binding phase, indicating that approximately half of the center P sites bound stigmatellin more slowly and in a different position relative to the b(L) heme, generating a different effect on its electronic environment. Significantly, the slow stigmatellin binding phase was lost as the inhibitor concentration was increased. This implies that a conformational change is transmitted from one center P site in the dimer to the other upon stigmatellin binding to one monomer, rendering the second site less accessible to the inhibitor. Because the position that stigmatellin occupies at center P is considered to be analogous to that of the quinol substrate at the moment of electron transfer, these results indicate that the productive enzyme-substrate configuration is prevented from occurring in both monomers simultaneously.
File Format	PDF HTM / HTML
Alternate Webpage(s)	http://www.dartmouth.edu/~blt/Publications/JBC282,22289.pdf
PubMed reference number	17561507v1
Volume Number	282
Issue Number	31
Journal	The Journal of biological chemistry
Language	English
Access Restriction	Open
Subject Keyword	Achromobacter denitrificans Electron Transport Complex III Heme Paracoccus yeei Phase II/III Trial disease transmission hydroquinone monomer myxothiazol oxidation respiratory chain complex III location respiratory electron transport chain process stigmatellin ubiquinol
Content Type	Text
Resource Type	Article