Figure 1.

Calcium transport in IOVs made from erythrocytes. The ATP-dependent Ca²⁺ uptake is demonstrated as a function of free-Ca²⁺ concentration. One hundred micrograms of membrane protein was preincubated in the transport medium containing the desired free-Ca²⁺ concentration at 37°C with (B) or without 10 μg/ml of calmodulin (A) for 5 min. The reaction was started with 0.5 mM ATP and incubated for a further 10 min. The experimental groups are indicated in the figure. Brother designates the neurologically intact compound heterozygote brother. Four independent IOV preparations and Ca²⁺ transport measurements gave similar results. The V_max of the calmodulin dependent Ca²⁺ pump was significantly higher (P < 0.05) in the IOVs prepared from the erythrocytes of the propositus than the V_max measured in IOVs from the erythrocytes from the control or other members of the family. Data represent the results of one typical experiment (n = 4).