| Assay Method Information | |
| | Filter-paper Assay |
| Description: | This assay relies on Whatman P-81 filter paper, which binds peptides but not SAM. Protein Methyl Transferases (PMTs) transfer 3H-Me of [3H-Me]-SAM to peptide substrates and the resultant 3H-methylated, filter-paper-bound peptide is quantified with a scintillation counter. Briefly, 6 μL of the methylation reaction was spotted onto Whatman P-81 phosphocellulose filter paper (1.2×1.2 cm2) to immobilize the 3H-labeled peptide. After drying in air for 20 min, the filter paper was immersed into 20 mL of 50 mM Na2CO3/NaHCO3 buffer (pH=9.2), and washed 5 times for 10 min each time. The washed filter paper was then transferred to a 20 mL scintillation vial containing 1 mL of distilled water and 10 mL of Ultima Gold scintillation cocktail or 7 mL scintillation vial containing 0.5 mL od distilled water and 5 mL of scintillation cocktail (PerkinElmer). The radioactivity was quantified by a Beckman LS6000IC liquid scintillation counter. |
| Affinity data for this assay | |
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