Fig. 4. Co-immunoprecipitation of native RyR with snapin. Native RyR was first immunoprecipitated (IP) with an appropriate antibody from solubilised (A) cardiac (2 mg) or skeletal muscle heavy SR (200 µg), or (B) synaptosomes (2 mg), and was subsequently incubated with radiolabelled, TNT-expressed snapin. Co-precipitated snapin was then analysed by autoradiography (15% SDS-PAGE gels). The first two lanes, showing 10% and 1% respectively, of the TNT reaction processed in the co-IPs provide a molecular weight standard and also enable estimation of co-immunoprecipitated snapin.