Analysis of a 5S RNA–protein complex isolated from the ribosomes of rye embryos

Abstract

Rye embryo ribosomes were dissociated into subunits and the large subunit fraction was treated with formamide. A low molecular weight complex of RNA and protein (RNP) was released. Electrophoresis of the RNP in polyacrylamide gels containing sodium dodecyl sulphate yielded an RNA band and a single protein band. The protein had a molecular weight of approximately 41 000 and the RNA of the complex was shown to be 5S ribosomal RNA.Embryos were germinated in the presence of [32P]orthophosphate and the labelled RNP was isolated from their ribosomes. The RNA component was partially digested with pancreatic A ribonuclease and the parts protected from degradation by the protein were determined by sequence analysis. Although the whole 5S RNA molecule was shielded to some extent, the portion most protected was between nucleotides 68 and 108. This is, therefore, probably the part of plant cytosol 5S RNA which is primarily involved in the interaction with protein in the complex and possibly in the ribosome as well.