JF549-Cys-LPETGG

JF549-Cys-LPETGG: Thiol-Linked Fluorescent Sortase A Substrate

JF549-Cys-LPETGG is a fluorescently labeled peptide containing the Sortase A recognition sequence LPETGG. Unlike conventional N-terminal amine-labeled LPETGG peptides, this product is prepared by reacting Cys-LPETGG with JF549-maleimide. The maleimide group reacts with the sulfhydryl group of the N-terminal cysteine, forming a covalent thioether linkage between JF549 and the peptide.

The resulting structure preserves the LPETGG Sortase A recognition motif while positioning the fluorescent dye through a cysteine-based conjugation handle. This defined conjugation strategy may be useful for researchers who require a thiol-derived linker architecture, comparison of labeling chemistries, or a fluorescent LPETG donor substrate for Sortase A-mediated protein modification.

Maleimide-Cysteine Conjugation

Maleimide chemistry is widely used for selective modification of cysteine-containing peptides. During preparation of this product, the thiol group of the N-terminal cysteine reacts with JF549-maleimide to generate a fluorescent thioether-linked peptide conjugate.

This conjugation route differs from direct labeling of the peptide's terminal amino group with an NHS-activated dye. The cysteine residue serves as a dedicated chemical attachment site, allowing the LPETGG region to remain available as the enzymatic recognition portion of the molecule.

Sortase A Recognition and Ligation

Staphylococcus aureus Sortase A recognizes the consensus sequence LPXTG, where X may be a compatible amino acid. In the LPETGG sequence, Sortase A recognizes the LPETG region and cleaves the peptide bond between threonine and the first glycine.

The enzyme forms an acyl-enzyme intermediate that can subsequently react with an appropriate N-terminal oligoglycine nucleophile. This reaction enables site-selective transfer of the fluorescent peptide segment to a compatible protein, peptide, antibody, biomaterial, or other engineered target.

Potential Applications

• Sortase A-mediated fluorescent labeling: Enzymatic attachment of a JF549-containing peptide segment to compatible oligoglycine-modified targets.
• Site-specific protein modification: Preparation of fluorescent proteins, recombinant constructs, antibody fragments, or peptide-protein conjugates.
• Live-cell and fluorescence imaging research: Detection of labeled biomolecules using microscopy or compatible fluorescence instrumentation.
• Flow cytometry: Fluorescent analysis of cells or particles modified through Sortase A-mediated conjugation.
• Biomaterial functionalization: Installation of fluorescent peptide tags onto engineered surfaces, hydrogels, nanoparticles, or scaffolds.
• Conjugation-method comparison: Evaluation of cysteine-maleimide labeling versus N-terminal amine labeling of LPETGG substrates.
• Sortase assay development: Use as a fluorescent donor substrate in reaction optimization, enzyme screening, or analytical assay development.

JF549 Fluorescent Label

JF549 is a bright, photostable fluorophore suitable for fluorescence microscopy, cellular imaging, flow cytometry, and other fluorescence-based detection methods. Its spectral characteristics are generally compatible with common orange-red fluorescence detection configurations.

Researchers should confirm excitation and emission settings using the specifications of their instrument and the dye documentation applicable to their experimental system.

Relationship to Other LPETG-Series Products

LifeTein offers complementary fluorescent products for constructing and studying Sortase A-mediated ligation systems:

• JF549-LPETGG — an LPETGG donor substrate in which JF549 is attached through the peptide's N-terminal amino group.
• JF549-Cys-LPETGG — the current product, prepared by conjugating Cys-LPETGG with JF549-maleimide through the cysteine thiol.
• JF549-GGGG-Cys — a fluorescent oligoglycine-containing reagent prepared by maleimide conjugation to the cysteine residue and designed as a complementary component for Sortase-related research.

Choosing Between the LPETG-Series Products

Custom Peptide and Sortase Reagents

LifeTein provides custom synthesis of LPETG-containing peptides, oligoglycine peptides, fluorescent conjugates, biotinylated substrates, linker-modified peptides, and other reagents for Sortase-mediated ligation research. Custom options may include alternative fluorophores, spacers, terminal modifications, peptide lengths, purity levels, and production scales.

Please contact LifeTein to discuss custom JF549-labeled peptides, LPXTG substrates, oligoglycine nucleophiles, or matched reagent sets for your specific Sortase A workflow.

For research use only. Not for human, veterinary, diagnostic, therapeutic, or clinical use.