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Inhibitory specificity and potency of proSAAS-derived peptides toward proprotein convertase 1
1Laboratories of Molecular Medicine and Diseases of Ageing Center, Loeb Health Research Institute, The Ottawa Hospital, Ottawa, Ontario K1Y 4K9, Canada. abasak@lri.ca
The Journal of Biological Chemistry
|July 4, 2001
Summary
The neuroendocrine protein proSAAS inhibits prohormone convertase 1 (PC1) activity. Specific peptide sequences within proSAAS, particularly proSAAS-(235-244), are potent PC1 inhibitors, with key amino acids driving this inhibition.
Area of Science:
- Biochemistry
- Neuroendocrinology
Background:
- Prohormone convertase 1 (PC1) is crucial for processing neural and endocrine precursors.
- The neuroendocrine protein proSAAS is implicated in regulating PC1 activity.
- PC1 inhibitory sequences in proSAAS are localized near its C terminus, featuring a KR(244) motif.
Purpose of the Study:
- To identify and characterize the specific inhibitory sequences of proSAAS against PC1.
- To determine the contribution of individual amino acid residues to PC1 inhibition potency and specificity.
- To investigate the structural basis of proSAAS-mediated PC1 inhibition.
Main Methods:
- Peptide synthesis and characterization of proSAAS fragments.
- Enzyme inhibition assays to determine inhibitor constants (K(i)) and substrate cleavage.
- Alanine and lysine scanning mutagenesis to probe residue contributions.
- Molecular modeling and circular dichroism spectroscopy for structural analysis.
Main Results:
- The decapeptide proSAAS-(235-244) is a potent reversible competitive PC1 inhibitor (K(i) ≈ 9 nm).
- Specific residues, including P1 Arg, P2 Lys, and P4 Arg, are critical for PC1 inhibition.
- Structural analysis suggests an extended, poly-L-proline II conformation for the potent inhibitor proSAAS-(235-244).
Conclusions:
- The C-terminal region of proSAAS contains potent PC1 inhibitory sequences.
- The potency and specificity of PC1 inhibition are modulated by specific amino acid residues and peptide conformation.
- Understanding these interactions provides insights into neuroendocrine precursor processing regulation.