Fig. 1.

PCSK3 preferentially cleaves proapelin into apelin-13. Proapelin produced and purified from E. coli was incubated with recombinant PCSK3. (A) Proapelin and its fragments alongside predicted molecular weights and numbered 1–3 according to elution time. The gray Ser at the N-terminus is retained residue following TEV protease cleavage; the green residues represent the endogenous 42 amino acid N-terminal pro-domain; blue represents the 13 residue apelin-13, with 1* being Pyr-apelin-13. Proapelin incubation with PCSK3 resulted in production of 3 new products corresponding to apelin-13, Pyr-apelin-13, and the 43 amino acid N-terminal pro domain at (B) pH 7 (C) pH 6 and (D) pH 5. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)