Proton coupling is preserved in membrane-bound chloroplast ATPase activated by high concentrations of tentoxin.
The effect of tentoxin at high concentrations was investigated in thylakoids and proteoliposomes containing bacteriorhodopsin and CF0CF1. Venturicidin-sensitive ATP hydrolysis, ATP-generated delta pH and ATP synthesis were practically 100% inhibited at 2 microM tentoxin, and restored to various extents beyond 50 microM. With respect to the native enzyme, tentoxin-reactivated ATPase had the following properties: (i) a higher delta pH requirement to synthetise ATP; (ii) a decreased futile proton flow through CF0CF1 (without ADP), which remains 100% blocked by ADP. It is concluded that despite its altered kinetic performances, tentoxin-modified CF0CF1 preserves its mechanism and remains a tightly coupled proton pump.
Sigalat
C
C
Section de Bioénergétique, DBCM-CEA Saclay, Gif-sur-Yvette, France.
Pitard
B
B
Haraux
F
F
D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism; D001436:Bacteriorhodopsins / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000201:enzymology; D002736:Chloroplasts / Q000201:enzymology*; D004789:Enzyme Activation; D006868:Hydrolysis / Q000187:drug effects; D008081:Liposomes / Q000378:metabolism; D010456:Peptides, Cyclic / Q000494:pharmacology*; D011510:Proteolipids / Q000187:drug effects / Q000378:metabolism; D017494:Proton Pumps / Q000378:metabolism*; D006180:Proton-Translocating ATPases / Q000378:metabolism*; D014698:Venturicidins / Q000494:pharmacology
D008081:Liposomes; D010456:Peptides, Cyclic; D011510:Proteolipids; D017494:Proton Pumps; D014698:Venturicidins; C020485:proteoliposomes; D001436:Bacteriorhodopsins; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; C003384:tentoxin