Figure 2.

The 8VM1 and 8VP1 deoxyribozymes covalently modify phosphotyrosine and phosphoserine. (a) PAGE image showing high selectivity for Tyr^P over Tyr^OH and for Ser^P over Ser^OH (50 mM HEPES, pH 7.5, 40 mM Mg²⁺, 20 mM Mn²⁺, 150 mM NaCl, 37 °C; single-turnover assays). Representative time points at 0, 0.5, 4, 24 h. Open arrowhead: 3′-³²P-radiolabeled RNA substrate. Filled arrowhead: DNA-anchored hexapeptide attached to RNA. Each peptide was attached to the oligonucleotide anchor via its amino terminus and a short (8VM1) or long (8VP1) tether; see Supporting Information. Each product identity was verified by MALDI mass spectrometry (see Experimental Section). (b) Kinetic data for the tagging reactions. k_obs (top to bottom for plots) = 0.37, 0.17, 0.15, 0.095 h⁻¹. For 8VP1 (but not 8VM1), 2–4% product in 50 h is observed when the Y^P or S^P hexapeptide is unattached to the DNA anchor, i.e., a free hexapeptide substrate (data not shown).