Fig. 1.

Inhibition by tentoxin of background ATPase activity in chloroplasts. Chloroplasts were incubated at room temperature in the dark for 10 min in IB containing tentoxin as indicated. ATP mixed with [γ-³²P]-ATP was then added to final concentration of 1 mM. Samples were withdrawn at 0 and 30 min after adding ATP. Reactions were stopped by adding an ice-cold acidic charcoal solution. After separating Pi from ATP and other nucleotides using charcoal (Materials and Methods), released [³²P] was quantified by scintillation counting. Each point on the graph is the mean of at least three replicates; error bars represent SD.