Protein
synthesis and degradation responding to environmental cues
is critical for understanding the mechanisms involved. Chemical proteomics
introducing bioorthogonal tagging into proteins and isolation by biotin
affinity purification is applicable for enrichment of newly synthesized
proteins (NSPs). Current enrichment methods based on biotin–streptavidin
interaction lack efficiency to release enriched NSPs under mild conditions.
Here we designed a novel method for enriching newly synthesized peptides
by click chemistry followed by release of enriched peptides via tryptic
digestion based on cleavable bioorthogonal tagging (CBOT). CBOT-modified
peptides can further enhance identification in mass spectrometry analysis
and provide a confirmation by small mass shift. Our method achieved
an improvement in specificity (97.1%) and sensitivity for NSPs in
cell lysate, corresponding to profiling at a depth of 4335 NSPs from
2 mg of starting materials in a single LC-MS/MS run. In addition,
the CBOT strategy can quantify NSPs when coupling a pair of isotope-labeled
azidohomoalanine (AHA/hAHA) with decent reproducibility. Furthermore,
we applied it to analyze newly synthesized proteomes in the autophagy
process after 6 h rapamycin stimulation in cells, 2910 NSPs were quantified,
and 337 NSPs among them were significantly up- and down-regulated.
We envision CBOT as an effective and alternative approach for bioorthogonal
chemical proteomics to study stimuli-sensitive subsets.