Nitrilase-Activatable Noncanonical Amino Acid Precursors for Cell-Selective Metabolic Labeling of Proteomes

Cell-selective
protein metabolic labeling is of great interest
for studying cell–cell communications and tissue homeostasis.
We herein describe a nitrilase-activatable noncanonical amino acid
tagging (NANCAT) strategy that exploits an exogenous nitrilase to
enzymatically convert the nitrile-substituted precursors to their
corresponding noncanonical amino acids (ncAAs), l-azidohomoalanine
(Aha) or homopropargylglycine (Hpg), in living cells. Only cells expressing
the nitrilase can generate Aha or Hpg in cellulo and
metabolically incorporate them into the nascent proteins. Subsequent
click-labeling of the azide- or alkyne-incorporated proteins with
fluorescent probes or with affinity tags enables visualization and
proteomic profiling of nascent proteomes, respectively. We have demonstrated
that NANCAT can serve as a versatile strategy for cell-selective labeling
of proteomes in both bacterial and mammalian cells.