Figure 7.
High affinity for ATP. Vesicles were isolated from ECA1-transformed mutants for ATP- or GTP-dependent 45Ca transport. Reaction mixtures contained 0.1 μm free Ca2+, 5 μm gramicidin, 0.5 μm bafilomycin, and 25 μm to 3 mm ATP (•) or GTP (○). Uptake was measured at 40 s. Apparent ATP Km values were 20 and 235 μm. The results are the averages of three experiments. conc., Concentration.