ActivX™ Desthiobiotin-GTP Probes contain a modified biotin attached to the nucleotide by a labile acyl-phosphate bond. ActivX active-site enrichment probes are advantageous for determining active enzyme levels through the use of analog-tagged probes to allow profiling of both inactive and active enzymes. The ActivX probes selectively enrich only those enzymes that are functionally active and biologically relevant at the time of labeling. With selective enrichment, one can identify and profile target enzyme classes across samples or can assess the specificity and affinity of enzyme inhibitors.

After removal of GTP or GDP nucleotides from enzymes, the desthiobiotin-GTP probe can be used to covalently modify conserved lysine residues in the GTPase nucleotide-binding site. Desthiobiotin-GTP can selectively enrich, identify and profile target enzyme classes in samples. Pre-incubation of samples with small-molecule inhibitors that compete with active-site probes can be used to determine inhibitor binding affinity and target specificity. The ActivX Desthiobiotin-GTP Probe covalently labels the active site of GTPases and GTPase subunits of G-protein coupled receptors.

Applications of ActivX Desthiobiotin-GTP Probe:
• Broad enrichment of GTP-binding proteins from tissues, cells and sub-cellular proteomes
• Enrichment of enzymes based on function
• Profiling of dozens to hundreds of inhibitor targets

Assessment of active-site labeling with desthiobioin probes can be accomplished by either Western blot or mass spectrometry (MS). For the Western blot workflow, desthiobiotin-labeled proteins are enriched for SDS-PAGE analysis and subsequent detection with specific antibodies. For the MS workflow, desthiobiotin-labeled proteins are reduced, alkylated and enzymatically digested to peptides. Only the desthiobiotin-labeled, active-site peptides are enriched for analysis by LC-MS/MS. Both workflows can be used for determining inhibitor target binding, but only the MS workflow can identify global inhibitor targets and off-targets.

These products are subject to a limited use label license.