Specific heterodimer formation by the cytoplasmic domains of the b and b ` subunits of cyanobacterial ATP synthase

Autor(en): Dunn, SD
Kellner, E
Lill, H
Stichwörter: 2ND STALK; Biochemistry & Molecular Biology; CHLOROPLASTS; COMPLEX; DELTA-SUBUNIT; DIMERIZATION; ESCHERICHIA-COLI F1F0-ATPASE; F-0 SECTOR; PURIFICATION; RHODOBACTER-CAPSULATUS; RHODOSPIRILLUM-RUBRUM
Erscheinungsdatum: 2001
Herausgeber: AMER CHEMICAL SOC
Journal: BIOCHEMISTRY
Volumen: 40
Ausgabe: 1
Startseite: 187
Seitenende: 192
Zusammenfassung: 
The soluble domains of the b and b' subunits of the ATP synthase of the cyanobacterium Synechocystis PCC 6803 were expressed with His tags attached to their N-termini. Following purification, the polypeptides were characterized by chemical cross-linking, analytical ultracentrifugation, and circular dichroism spectroscopy. Treatment of a mixture of the soluble b and b' domains with a chemical crosslinking agent led to substantial formation of cross-linked dimers, whereas similar treatment of either domain by itself resulted in only trace formation of cross-linked species. The molecular weights of the domains of b and b' in solution at 20 degreesC, measured by sedimentation equilibrium, were 17 800 /- 700 and 16 300 /- 400, respectively, compared to calculated polypeptide molecular weights of 16 635 and 15 422, whereas a mixture of b and b' gave a molecular weight of 29 800 /- 800. The sedimentation coefficient of an equimolar mixture was 1.73 /- 0.03. The circular dichroism spectra of the individual polypeptides indicated helical contents in the range of 40-50%; the spectrum of the mixture revealed changes indicative of coiled-coil formation and a helical content of 60%. The results indicate that the cytosolic domains of the b and b' subunits exist individually as monomers but form a highly extended heterodimer when they are mixed together.
ISSN: 00062960
DOI: 10.1021/bi001821j

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