The ATP synthase gamma subunit provides the primary site of activation of the chloroplast enzyme: experiments with a chloroplast-like Synechocystis 6803 mutant.
The activation characteristics of the F1Fo-ATP synthase (where F1 and Fo are the hydrophilic and membrane-bound parts respectively of the enzyme) from Synechocystis 6803 wild-type and a Synechocystis 6803 mutant with a chloroplast-like insertion in the gamma subunit have been studied. Activation of the ATP synthase in wild-type and mutant membrane vesicles was performed by acid-base transition-induced generation of a proton motive force (Delta mu H+). Since the mutant containing the regulatory segment of the chloroplast gamma subunit showed thiol-modulation (typical of the chloroplast enzyme), this segment is indeed involved in the regulation of enzyme activation. It is shown that the ATP synthase from Synechocystis 6803 wild type corresponds functionally to the reduced form of the chloroplast ATP synthase, in view of the low Delta mu H+ required for activation of the enzyme and the high stability of the active state. Both the cyanobacterial wild-type and mutant ATP synthases can be activated by methanol, which apparently does not require the presence of the gamma subunit regulatory segment.
Krenn
B E
BE
Institute of Molecular Biological Sciences, BioCentrum Amsterdam, Vrije Universiteit, De Boelelaan 1087, 1081 HV Amsterdam, The Netherlands.
Strotmann
H
H
Van Walraven
H S
HS
Scholts
M J
MJ
Kraayenhof
R
R
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002736:Chloroplasts / Q000201:enzymology*; D000458:Cyanobacteria / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D003553:Cystine / Q000737:chemistry; D004789:Enzyme Activation / Q000528:radiation effects; D006868:Hydrolysis; D008027:Light; D010084:Oxidation-Reduction; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006180:Proton-Translocating ATPases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013816:Thermodynamics
D001426:Bacterial Proteins; D010940:Plant Proteins; D003553:Cystine; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases