title: Binding of Met-tRNAf to native 40 S ribosomal subunits in Ehrlich ascites tumor cells.
abstract: Two forms of native 40 S ribosomal subunits, distinguishable by their buoyant densities, are recovered from Ehrlich ascites cells. In this communication, we describe experiments designed to test whether Met-tRNAf is associated with either form. Our results indicate that (a) in the cell, Met-tRNAf is bound to the native 40 S subunit, and in particular, to the subunit of density 1.40 g x cm-3; (b) under the growth conditions used, less than 10% of the low density native subunits have bound Met-tRNAf; (c) the majority of the Met-tRNAf containing native 40 S subunits, isolated from sucrose gradient analyses of cell extracts, join with 60 S subunits in vitro to form 80 S monosomes only if additional ribosomal wash factors are provided; and (d) the 80 S monosomes so formed are completed initiation complexes that can form peptide bonds. These results support the hypothesis that various forms of the native 40 S subunit represent different stages in the formation of a complete initiation complex.
mesh_terms: D000604:Amino Acyl-tRNA Synthetases; D000818:Animals; D001665:Binding Sites; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D005561:Formates; D008099:Liver; D008274:Magnesium; D008715:Methionine; D051379:Mice; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors; D012333:RNA, Messenger / Q000378:metabolism; D012334:RNA, Neoplasm / Q000378:metabolism; D012335:RNA, Ribosomal / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D051381:Rats; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D005561:Formates; D010448:Peptide Initiation Factors; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D012335:RNA, Ribosomal; D012343:RNA, Transfer; D008715:Methionine; D000604:Amino Acyl-tRNA Synthetases; D008274:Magnesium