AN ARGUMENT FOR THE EXISTENCE OF A NATURAL COMPLEX BETWEEN PROTEIN L5 AND 5 S RNA IN RAT-LIVER 60-S RIBOSOMAL-SUBUNITS

Electrophoresis of the 60S ribosomal subunits from rat liver in the presence of citrate ions removes the 7S ribonucleoprotein complex between protein L5 and 5S RNA, although this complex is not released by dialysis or by centrifugation through a sucrose cushion in the same buffer. Using acetate instead of citrate, the subunits remain intact in all cases. In the presence of EDTA, the complex is always released. The poly(U) [polyuracil] directed polyphenylalanine synthesis is correlated in each case with the presence of this complex within the subunits. The melting curves of subunits which have been treated with citrate, acetate or EDTA and then taken back in the buffer in which they were stored suggest that the specific RNA-protein interactions are preserved in the presence of acetate and of citrate but not of EDTA. The interpretation that the association of protein L5 and 5S RNA exists within the active subunits is supported.