Fig. 2. (A) Co-crystal structure of TCO-SCH with ERK2 (pdb:6GJD). The binding mode of the inhibitor core was conserved compared with the unmodified inhibitor SCH772984. (B) The amide linker of TCO-SCH likely encountering a steric clash with the protein is highlighted. (C) Co-crystal structure of TCO-GDC-2 with ERK2 (pdb:; 6GJB). The more slender alkyne linker provides a suitable vector to position the TCO tag in the solvent with a minimal steric clash with the protein.