Table I.

An increase in CRT levels increases ATP-dependent45Ca2+ accumulation of ER-enriched membranes in vitro

Cell TypeRecovered45Ca2+
nmol45Ca2+ mg protein−1
Wild type10.0 ± 0.2
Nt CRT:714.1 ± 0.2
Heat-shocked wild type11.1 ± 0.7
Heat-shocked NtCRT:722.2 ± 2.2

ER-enriched membranes vesicles (fraction 2, Fig. 1), were obtained from heat-shocked and non-heat-shocked CRT transgenic and wild-type cell lines as indicated in “Materials and Methods.” ATP-dependent 45Ca2+ uptake was performed on the ER-enriched vesicles and terminated after a 20-min incubation. The ATP-dependent 45Ca2+ uptake was measured in the presence and absence of 3 mM ATP, and is shown as the amount accumulated of 45Ca2+ per milligram protein after subtraction of control values (absence of ATP). Data (mean of two values ± range) are shown from one experiment. The experiment has been repeated at least three times with consistent results.