Biotin-Ahx-LPETGS-NH2

Biotin–aminohexanoic acid–LPETGS–NH₂ is a synthetic peptide used extensively in sortase A–mediated transpeptidation assays and proximity-based cell interaction studies, notably in the LIPSTIC (Labeling Immune Partnerships by SorTagging Intercellular Contacts) methodology.

The LPETGS motif belongs to the LPXTG sequence family recognized by Sortase A (SrtA) from Staphylococcus aureus—a membrane-associated enzyme that cleaves specifically between the threonine and glycine residues in the LPXTG motif. This reaction yields a reactive thioester intermediate that can be resolved by attack from an oligoglycine nucleophile, enabling site-specific ligation of biomolecules.

Applications:

1. Cell-Cell Interaction Mapping (LIPSTIC)

• In the LIPSTIC system, biotin-Ahx-LPETGS serves as the donor substrate: cells engineered to express Sortase A on their surface transfer this biotinized peptide to adjacent cells expressing an oligoglycine acceptor tag fused to a receptor or ligand.
• This strategy allows direct marking of contacting cells, which can later be recovered and analyzed via flow cytometry or immunoprecipitation.

2. Protein Engineering and Labeling

• Separate from LIPSTIC, LPETG-based peptides (including LPETGS) are widely used to site-specifically tag proteins or antibodies with biotin, fluorescent dyes, or other probes using sortase-mediated ligation.

Advantages of This Peptide Design:

• Biotin modification provides an exceptionally strong, non-covalent affinity to streptavidin or neutravidin, facilitating highly sensitive detection or streptavidin-based pull-down assays.
• The Ahx spacer (6‑aminohexanoic acid) ensures that the biotin tag is sufficiently distanced from the LPETGS core motif, reducing steric hindrance during enzymatic conjugation or receptor binding.
• The terminal amide (–NH₂) stabilizes the C-terminus to prevent carboxylate interference in enzymatic processing or charge-based artifacts.
• Mechanistic studies of immune cell interactions: LIPSTIC enables researchers to capture and quantify receptor–ligand encounters between living cells in vivo, shedding light on dynamic immune synapses.
• Versatility across biological settings: The peptide is adaptable to diverse receptor-ligand systems as long as one partner is engineered to express Sortase A and another carries glycine residues that function as nucleophiles.
• Precision and specificity: Sortase-based ligation produces site-specific modifications without general chemical reactivity, lowering background labeling and enhancing reproducibility.

Biotin-Ahx-LPETGS-NH2 is a 32-residue synthetic peptide with the sequence Leu-Pro-Glu-Thr-Gly-Ser-Asn-His-Ala-Cys-Ile-Asp-Leu-Pro-Glu-Thr-Gly-Ser-Leu-Pro-Glu-Thr-Gly-Ser-Leu-Pro-Glu-Thr-Gly-Ser-Asn-His. Biotin provides an affinity handle for streptavidin-based capture or detection; the Ahx spacer separates the peptide sequence from an attached label or affinity handle; C-terminal amidation removes the terminal carboxylate charge. The sequence contains 1 cysteine residue, which can support thiol-selective conjugation or disulfide chemistry when the thiol is available; contains multiple acidic residues (1 Asp and 4 Glu), contributing negative charge at neutral pH. No specific receptor, enzyme, pathway, disease association, or biological activity is assigned without product-specific experimental evidence.

• streptavidin-based capture or detection
• binding and pull-down assay development
• thiol-selective conjugation or immobilization studies
• LC-MS/HPLC analytical method development
• sequence-specific assay controls

Sequence-derived chemical properties are provided to support reagent selection and experimental planning. They do not establish a biological function. Solubility, aggregation, adsorption, conjugation efficiency, and assay performance should be validated under the intended experimental conditions.