title: Ribosomal proteins L7/L12 of Escherichia coli. Localization and possible molecular mechanism in translation.
abstract: Experiments were performed in order to determine the minimal requirement for the proteins L7/L12 in polyphenylalanine synthesis and elongation factor EF-G-dependent GTP hydrolysis. Via reconstitution, ribosomal particles were prepared containing variable amounts of L7/L12. The L7/L12 content of these particles was carefully determined by the use of 3H-labelled L7/L12 and by radioimmunoassay. The activity of the particles was determined as a function of the L7/L12 content. Our results show that only one dimer of L7/L12 is required for full activity in EF-G-dependent GTP hydrolysis. On the other hand, two L7/L12 dimers are required for polyphenylalanine synthesis. In addition, we have determined the relation between the number of L7/L12 stalks, as observed by electron microscopy, and the L7/L12 content of the 50 S particles. Our interpretation of these results is that each ribosomal particle possesses two L7/L12 binding sites, each site being involved in binding one dimer. Binding of L7/L12 dimer in one site gives rise to formation of the L7/L12 stalk, whereas binding in the other site has no effect on the number of visible stalks.
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D004926:Escherichia coli / Q000235:genetics* / Q000648:ultrastructure; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D008854:Microscopy, Electron; D010452:Peptide Biosynthesis; D010445:Peptide Elongation Factors / Q000378:metabolism; D010455:Peptides; D014176:Protein Biosynthesis; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D010445:Peptide Elongation Factors; D010455:Peptides; D012269:Ribosomal Proteins; C012001:polyphenylalanine; C016700:ribosomal protein L7-L12; D006160:Guanosine Triphosphate; D020963:GTP Phosphohydrolase-Linked Elongation Factors