PRECISE DETERMINATION OF RNA-PROTEIN CONTACT SITES IN THE 50 S RIBOSOMAL-SUBUNIT OF ESCHERICHIA-COLI

RNA-protein cross-linked complexes were isolated and purified to obtai n precise data about RNA-protein contact sites in the 50 S ribosomal s ubunit of Escherichia coli. N-terminal microsequencing and matrix-assi sted laser desorption ionization MS were used to identify the cross-li nking sites at the amino acid and nucleotide levels. In this manner th e following contact sites of five ribosomal proteins with the 23 S rRN A were established: Lys-67 of L2 to U-1963, Tyr-35 of L4 to U-615, Lys -97 of L21 to U-546, Lys-49 of L23 to U-139 or C-140 and Lys-71 and Ly s-74 of L27 to U-2334.