ActivX Desthiobiotin-ATP or ADP Probes are nucleotide derivatives that covalently modify the active site of enzymes at conserved lysine residues in the nucleotide binding site. The structure of these probes consists of a modified biotin (desthiobiotin) attached to the nucleotide through a labile acyl-phosphate bond. Desthiobiotin is a biotin analog that binds less tightly to biotin-binding proteins resulting in binding that is easily reversed by biotin displacement, low pH or heat denaturation.

ActivX active-site enrichment probes are advantageous for determining active enzyme levels using analog-tagged probes to allow profiling of both inactive and active enzymes. The ActivX ATP and ADP Probes covalently label the active site of ATPases, including chaperones and metabolic enzymes, to enable their selective enrichment using a desthiobiotin tag.

Desthiobiotin-ATP or ADP probes can be used to selectively enrich, identify and profile target enzyme classes or assess the specificity of enzyme inhibitors. Because many ATPases and other nucleotide-binding proteins bind nucleotides or inhibitors even when they are enzymatically inactive, the desthiobiotin probes allow profiling of both inactive and active enzymes in a complex sample. Preincubation of samples with small-molecule inhibitors that compete for active sites can be used to determine inhibitor binding affinity. Active-site nucleotide probes also can be used to identify inhibitor off-targets. With selective enrichment, one can identify and profile target enzyme classes across samples or can assess the specificity and affinity of enzyme inhibitors.

Applications of ActivX ATP and ADP Probes:
• Profile small-molecule binding affinities and active-site inhibition in a dose-dependent manner
• Identify dozens to hundreds of inhibitor targets and off-targets from tissues, cells and subcellular proteomes
• Enrichment of enzymes based on function

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.