The Composition and Properties of the Escherichia coli 5-S RNA-Protein Complex (original) (raw)

1982, European Journal of Biochemistry

At a high concentration of MgC12 (30 mM) and a low concentration of proteins from the 50-S subunit (0.2 mgiml), only three proteins, L15, L18 and L25, bind to 5-S RNA in significant amounts. On the other hand, in a buffer containing only 1 mM Mg C12, but otherwise at the same ionic strength (0.2 M), or at a protein concentration about 1 .5 mg/ml, a large, stable complex can form between immobilized 5-S RNA and 50-S ribosomal proteins. This complex contains proteins L2, L3, L5, L15, L16, L17, L18, L21, L22, L25, L33 and L34, and it possesses properties relevant to the function of the 50-S subunit: it has a binding site for deacylated tRNA, with a dissociation constant of 4.5 x M. The complex formed with 5-S RNA immobilized on an affinity column interacts also with 30-S subunits. The 5-S RNA-protein complex is interpreted as a sub-ribosomal domain which includes a considerable fraction of the peptidyl transferase center of the Escherichiu coli ribosome.