FIGURE 1.

The effect of Ca²⁺ and IP₃ on the formation of trypsin fragment V. Cerebellum microsomes were incubated for 5 min with 0.9 μm free Ca²⁺ and/or 10 μm IP₃ as indicated (A). The membranes were then digested with trypsin (4 μg/ml) for a further 5 min, and the samples were then analyzed by SDS-PAGE and immunoblotting with an Ab directed at the terminal 17 amino acids of the C terminus (CT-1 Ab) or an Ab raised to a peptide sequence in the intraluminal loop between TM -5 and -6 (IL-3 Ab) (B). Densitometric quantitation of blots in A from three separate experiments are shown (mean ± S.E.) (C). Quantitation was carried out using NIH ImageJ software. WB, Western blot.