Fig. 6. Tryptic digestion of the SR Ca²⁺ATPase. The oocytes were injected with cRNAs and radiolabeled as in Fig. 1. The microsomes from the oocytes were digested with trypsin (Worthington: L-1-tosylamide-2-phenylethy-chloromethyl-ketone-treated) at ratios of trypsin to protein of 0.01 and 0.1 on ice for 60 minutes. The digests were immunoprecipitated with antiserum to the SR Ca²⁺ ATPase (lanes 1-6) or to the ß-subunit of the Na⁺/K⁺ ATPase (lanes 7-9).