PRSS50 and viral infectious disease: Expression of peptides with an 8-amino acid deletion at the N-terminus (CT20) inhibited virus infection to a similar extent as full-length RAPEL (Fig. 3B, C), whereas expression of 8 N-terminal amino acids and 9 C-terminal amino acids (NT8 and CT9) failed to do so, indicating that the middle 11 amino acids (M11) are required for RAPEL function.