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[Pro9] Substance P is a full-length Substance P analog in which Gly9 is replaced by proline. The peptide retains the remaining native sequence and C-terminal Met-NH2.
[Pro9] Substance P is a well-characterized selective NK1 receptor agonist and ligand used in receptor binding, autoradiography and functional tachykinin studies.
Product Information
| Product Name | [Pro9] Substance P |
| Catalog No. | AS2564 |
| CAS No. | 104486-69-3 |
| Sequence | Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Pro-Leu-Met-NH2 |
| One-Letter Sequence | RPKPQQFFPLM |
| Peptide Length | 11 residues |
| Molecular Formula | C66H102N18O13S |
| Molecular Weight | Approximately 1387.7 Da |
| Key Substitution | Gly9 → Pro |
| C-Terminus | Amidated |
| Pharmacological Profile | Selective NK1 receptor agonist |
Pro9 Restricts the C-Terminal Substance P Backbone
Replacing Gly9 with Pro changes the local backbone geometry near the C-terminal receptor-recognition region. Gly is highly conformationally flexible, whereas Pro imposes substantial restrictions on peptide backbone angles.
This single substitution produces a Substance P analog with strong NK1 receptor selectivity, making [Pro9]-SP more useful for receptor-subtype studies than native Substance P when NK1-specific signaling is the experimental focus.
Quantitative NK1 Binding Data
Tritiated [Pro9]-Substance P has been characterized in rat brain membranes. Saturation experiments identified a single population of binding sites with a reported Kd of approximately 1.48 nM and Bmax of approximately 29.7 fmol/mg protein.
The same pharmacological studies found no meaningful agonist or antagonist activity at classical NK2 and NK3 receptor preparations.
We recommend keeping the 1.48 nM value tied to the rat brain membrane system rather than applying it directly to recombinant human NK1 receptor assays.
Research Applications
[Pro9] Substance P can support NK1 receptor binding, autoradiography, receptor distribution studies, tachykinin signaling and comparative NK1/NK2/NK3 pharmacology.
Frequently Asked Questions
Is [Pro9] Substance P selective for NK1?
Yes. Classical binding and functional studies characterize it as a highly selective NK1 ligand and agonist.
What binding affinity has been reported?
A Kd of approximately 1.48 nM was reported for tritiated [Pro9]-Substance P in rat brain membranes.
What is changed relative to native Substance P?
Gly9 is replaced by Pro.
Does [Pro9] Substance P activate NK2 or NK3 receptors?
Classical comparative assays found no significant agonist or antagonist activity at NK2 or NK3 receptor systems.