Mapping of the SPATC1L binding site on RIα by in vitro binding assay using purified GST-SPATC1L and His-RIα proteins consisting of regions 1-6. Purified GST protein only was used as a control. Binding was confirmed by immunoprecipitation using an anti-SPATC1L antibody followed by immunoblot analyses of RIα, detected using an anti-His antibody. In, input; Sup, supernatant; IP, immunoprecipitated protein. 