Interactions of normal and sph^1J mutant minispectrins with actin and protein 4.1R assessed by a GST pulldown assay. Minispectrin-4.1R (lanes 1-4): 4.1R binds equally to both the normal and mutant minispectrins and does not bind to GST alone or to the GSH beads. Minispectrin-actin (lanes 5-8): The results show a slight interaction of the normal minispectrin with actin (more actin is bound in lane 5 than in lane 6). The mutant minispectrin does not interact (ie, the amount of actin bound is the same as the nonspecific binding observed in the controls). Minispectrin-actin-4.1R (lanes 9-12): A large amount of actin binds to the normal minispectrin (lane 9, black arrow), but only a small amount binds to the minispectrin lacking the C-terminal 13 amino acids of the α-spectrin EF domain (lane 10, white arrow).