Inhibition of Lu-spectrin interaction by αR4. GST-tagged cytoplasmic domain of Lu was preincubated with increasing concentrations of His-tagged αR4 or His-tagged αR5 at room temperature for 30 minutes. Then the mixtures were added to the 96-well plate coated with spectrin. The binding of GST-tagged cytoplasmic domain of Lu was detected by anti-GST antibody. Note the progressive decrease of Lu binding to spectrin with the increasing concentrations of αR4 but not with αR5.