TABLE 2.

Alignment of sequences at the Hap cleavage sites

Cleavage siteSequence alignmenta
P5P4P3P2P1P1′P2′P3′P4′P5′
Primary 1036-37DQSLLNALEA
Secondary 1046-47KQAELTAETQ
Tertiary 1077-78DQSLFALEAA
Quaternary 1067-68KRAVFSDPLL
Peptide librarybMAXXXXXNALEAKK (biotin)
  • a The peptide bond where cleavage occurs is between the P1 and P1′ columns. According to nomenclature by Schechter and Berger (22), the residues N terminal to the cleavage site are labeled P1, P2,… Pn in the N-terminal direction, and the residues C-terminal to the cleavage site are labeled P1′, P2′… Pn′.

  • b The “X” represents any amino acid except Cys. The P′ residues were fixed based on the P1′ to P5′ sequence at the Hap primary cleavage site. The M and A residues at the N terminus were added in order to validate the first two residues in the N-terminal sequencing reaction of each peptide.