Characterization and properties of a 5S-RNA-protein complex released from heated 60S ribosomal subunits

When rat liver 60S ribosomal subunits were heated in phosphate buffer in the presence of MgCl2, 5S RNA was released in the form of a nucleoprotein complex (RNPH), which was isolated either by electrophoresis in polyacrylamide gel or centrifugation through a sucrose gradient. In addition to L5 several proteins of functional significance were identified in the complex: the acidic phosphoproteins P1-P2 and, as weaker spots, L3-L4, L6-L7 and L22. Most of these proteins were also found, but only as traces, in the RNPEDTA used as a control. RNPH was able to associate with 40S subunits. Our results support the interpretation that RNPH is located at the subunits' interface, at or near the peptidyl-transferase center.