Peptide Sequence Motifs

Peptide Sequence Motifs

Reference catalog of conserved sequence motifs in peptides and proteins, with their biological functions, structural roles, and significance for peptide drug design.

Protease Recognition Motifs

DPP-4 Cleavage Motifs

Dipeptidyl peptidase-4 (DPP-4/CD26) cleaves dipeptides from the N-terminus after Pro or Ala at position 2:

Motif	Sequence Context	Cleavage Rate	Drug Design Implication
Xaa-Pro↓	Ala-His-Pro↓	Fast	GLP-1 native site — Aib substitution blocks
Xaa-Ala↓	Glu-Gly-Ala↓	Moderate	GIP native site — modification required
Xaa-Ser↓	—	Very slow	Natural DPP-4 resistance
Xaa-Gly↓	—	Negligible	No cleavage — resistant motif

Blocking strategies: Aib at position 2, β-amino acids, D-amino acids, N-methylation.

Trypsin Cleavage Motifs

Trypsin cleaves C-terminal to Lys and Arg:

Motif	Sequence Context	Cleavage Rate	Protection Strategy
Xaa-Lys↓	—	Fast	Lys → ornithine, N-methylation
Xaa-Arg↓	—	Fast	Arg → citrulline, N-methylation
Xaa-Lys-Pro↓	—	Slow	Pro shields Lys from cleavage

Metalloprotease Motifs

Matrix metalloproteinases (MMPs) recognize specific sequences:

Motif	MMP	Cleavage Site	Functional Role
Pro-Leu↓Gly-Leu	MMP-1	Collagen	Fibrillar collagen cleavage
Pro-Gln↓Gly-Ile	MMP-2	Gelatin	Type IV collagen cleavage
Pro-Arg↓Gly-Leu	MMP-9	Gelatin	Basement membrane degradation

Signaling Motifs

Phosphorylation Sites

Motif	Kinase	Function	Consensus
Ser/Thr-Pro	CDK	Cell cycle	[S/T]PX[K/R]
Tyr-[Asp/Glu]	Receptor Tyr kinases	Signal transduction	pYXX[D/E]
Arg-Arg-X-Ser/Thr	PKA	cAMP signaling	R-R-X-[S/T]
[Ser/Thr]-X-Arg	PKC	Calcium signaling	[S/T]X[K/R]

SH2 Binding Motifs

Src Homology 2 domains recognize phosphorylated tyrosine motifs:

Motif	SH2 Domain	Affinity	Biological Role
pY-E-E-I	Grb2	High	Growth factor signaling
pY-D-E-P	PLCγ	High	Calcium signaling
pY-A-P-E	Src	High	Kinase regulation
pY-V-N-V	SHP-2	Moderate	Phosphatase recruitment

PDZ Binding Motifs

PDZ domains recognize C-terminal motifs:

Motif	PDZ Domain	Function
X-Ser/Thr-X-Val-COOH	PSD-95	Synaptic organization
X-Hydrophobic-X-Val-COOH	NHERF	Membrane trafficking

Structural Motifs

Disulfide Bond Patterns

Motif	Bond Pattern	Peptide Example	Structural Role
Cys-X-Cys	Cys₂-Cys₇	Oxytocin, vasopressin	N-terminal ring constriction
Cys-X-X-X-X-Cys	Cys₃-Cys₈	Insulin A chain	Inter/intra-chain crosslink
Cys-X-X-Cys	—	Defensins	β-hairpin stabilization
Cys-Gly-X-Cys	—	Conotoxins	Knottin fold

Helix-Capping Motifs

Motif	Position	Function	Example
Asn-cap	N-cap	Nucleates α-helix	T4 lysozyme
Gly-cap	N-cap	Flexible initiation	Cytochrome c
Pro-kink	Internal	Helix disruption	GPCR transmembrane
Schellman	C-cap	Terminate α-helix	Various

β-Turn Sequences

Motif	Turn Type	Structural Role
Pro-Gly	Type I/II	β-hairpin reversal
Asn-Gly	Type I	β-sheet edge
Asp-Gly	Type II’	Reversed turn
Pro-X-X-Gly	Type I	β-hairpin stabilization

Receptor Binding Motifs

GLP-1 Receptor Binding

Position	Motif	Function	Modification for Stability
7-13	His-Ala-Glu-Gly-Thr-Phe-Thr	Core binding	Retained in analogs
8	Ala-Glu	DPP-4 site	Aib blocks cleavage
15-21	Ser-Asp-Val-S-Ser-Tyr	Receptor contact	Modified for selectivity
22-26	Leu-Glu-Gln-Ala-Ala	Helix formation	Maintained

Insulin Receptor Binding

Region	Motif	Function
A1-A21	Intra-chain disulfides	Structural scaffold
B20-B30	Hydrophobic C-terminus	Receptor binding
B23-B26	Phe-Val-Asn-Gln	Core binding epitope

Melanocortin Receptor Binding

Motif	Receptor	Function
His-Phe-Arg-Trp	MC4R	Core agonist motif
Phe-Arg-Trp	MC3R/MC4R	Minimum active sequence
Asp-Phe-Arg-Trp	MC4R	Full agonist

Degradation-Prone Motifs

Deamidation Hotspots

Motif	Deamidation Rate	Half-Life (pH 7.4, 37°C)
Asn-Gly	Very fast	1-2 days
Asn-Ser	Fast	3-5 days
Asn-Ala	Moderate	7-10 days
Gln-Gly	Slow	14-21 days

Oxidation Hotspots

Motif	Oxidation Rate	Protection Strategy
Met-X-X-Met	Fast	Replace Met with Nle or Met(O)
Trp-Pro	Moderate	Replace Trp with 5-FTrp
Cys-Cys	Fast (disulfide)	Block with alkylation

Isomerization Hotspots

Motif	Isomerization Rate	Structural Impact
Asp-Gly	Very fast	IsoAsp formation
Asp-Ser	Fast	Charge alteration
Asp-Pro	Moderate	Backbone disruption

Motif Database References

Database	URL	Content
PROSITE	prosite.expasy.org	Protein domains, families, sites
InterPro	ebi.ac.uk/interpro	Protein classification
Pfam	ebi.ac.uk/pfam	Protein families
SCOP	scop.mrc-lmb.cam.ac.uk	Structural classification
CATH	cathwww.biochem.ucl.ac.uk	Protein domain hierarchy

References

1. Rawlings ND, et al. “MEROPS: the peptidase database.” Nucleic Acids Res 2023;51:D633-D641.
2. Sigrist CJ, et al. “PROSITE: a protein domain database.” Nucleic Acids Res 2013;41:D344-D348.
3. Hulo N, et al. “The PROSITE database.” Nucleic Acids Res 2006;34:D227-D230.
4. Puntervoll P, et al. “EMBOSS patterns: motif detection.” Bioinformatics 2003;19:1978-1980.
5. Attwood TK, et al. “PRINTS: a protein motif fingerprint database.” Nucleic Acids Res 2003;31:400-402.