The SAAS granin exhibits structural and functional homology to 7B2 and contains a highly potent hexapeptide inhibitor of PC1

Angus Cameron, Yolanda Fortenberry, Iris Lindberg

Research output: Contribution to journalArticle


Prohormone convertases (PCs) 1 and 2 are thought to mediate the proteolytic cleavage of many peptide precursors. Endogenous inhibitors of both PC1 and PC2 have now been identified; the 7B2 protein is a nanomolar inhibitor of PC2, while the novel protein proSAAS was recently reported to be a micromolar inhibitor of PC1 [Fricker et al. (2000) J. Neurosci. 20, 639- 648]. We here report evidence that 7B2 and proSAAS exhibit several elements of structural and functional homology. Firstly, 26 kDa human, mouse and rat proSAAS, like all vertebrate 7B2s, contain a proline-rich sequence within the first half of the molecule and also contain a C-terminal 40 residue peptide (SAAS CT peptide) separated from the remainder of the protein by a furin consensus sequence. The SAAS CT peptide contains the precise sequence of a hexapeptide previously identified by combinatorial peptide library screening as a potent inhibitor of PC1, and the vast majority of the inhibitory potency of proSAAS can be attributed to this hexapeptide. Further, like the 7B2 CT peptide, SAAS CT-derived peptides represent tight-binding competitive convertase inhibitors with nanomolar potencies. Lastly, recombinant PC1 is able to cleave the proSAAS CT peptide to a product with a mass consistent with cleavage following the inhibitory hexapeptide. Taken together, our results indicate that proSAAS and 7B2 may comprise two members of a functionally homologous family of convertase inhibitor proteins. (C) 2000 Federation of European Biochemical Societies.

Original languageEnglish (US)
Pages (from-to)135-138
Number of pages4
JournalFEBS Letters
Issue number2
StatePublished - May 12 2000



  • 7B2
  • Furin
  • Inhibitor
  • Prohormone convertase 1 and 2
  • SAAS granin

ASJC Scopus subject areas

  • Biophysics
  • Structural Biology
  • Biochemistry
  • Molecular Biology
  • Genetics
  • Cell Biology

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