Figure 8. Effect of CPZ on cleavage of the C-terminal tail.

Trypsin treatment, SDS-PAGE, and immunoblotting were performed as in Fig. 7. The effect of CPZ on accumulation of the C-terminal fragment was investigated at pH 8 in the presence of either Na⁺ or Gua⁺. Note the significant difference between Na⁺ and Gua⁺ on the accumulation of the 55 kDa fragment, occurring at the middle of the α-subunit (T₁ site, Ref. [29]). The anomalous migration of the 4 kDa peptide is possibly due to its polar properties and its small molecular mass. Note that, due to the difference in staining intensity, the upper part of the immunoblot was made less intense.