The codon on mRNA is recognized by the anticodon of tRNA rather than by the activated amino acid Cysteinyl-tRNA H O R H O Cysteine tRNACys synthetase HS-CH-C-C-0-tRNACYs nickel H一CH2-C-C-0-tRNA ATP+H,0 AMP+2 Pi NH Cys-tRNA YS Ala-tRNACY 1. Cys-tRNACyS is chemically converted to Ala-tRNACyS 2. Studies with in vitro protein synthesis systems proved that Ala-tRNA Cys will incorporate Ala at places of Cys using poly (G, t)as templates or hemoglobin mRNA as template (with [4Cl-Ala-tRNACys)The codon on mRNA is recognized by the anticodon of tRNA rather than by the activated amino acid 1. Cys-tRNACys is chemically converted to Ala-tRNACys ; 2. Studies with in vitro protein synthesis systems proved that Ala-tRNACys will incorporate Ala at places of Cys: using poly(G,U) as templates or hemoglobin mRNA as template (with [14C]-Ala-tRNACys)