title: The composition of an unusual precursor of 50 S ribosomes in a mutant of Escherichia coli.
abstract: Escherichia coli strain 15--28 is a mutant which during exponential growth contains large amounts of a '47S' ribonucleoprotein precursor to 50S ribosomes. The '47S particles' are more sensitive to ribonuclease than are 50S ribosomes. The 23 S RNA of 47S particles may be slightly undermethylated, but cannot be distinguished from the 23S RNA of 50S ribosomes by sedimentation or electrophoresis. Isolated particles have 10--15% less protein than do 50S ribosomes; proteins L16, L28 and L33 are absent. Comparison with precursor particles studied by other workers in wild-type strains of E. coli suggests that the assembly of 50S ribosomes in strain 15--28 is atypical.
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis; D002499:Centrifugation, Density Gradient; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D008970:Molecular Weight; D009154:Mutation; D009694:Nucleic Acid Precursors / Q000032:analysis*; D009698:Nucleoproteins / Q000032:analysis*; D012329:RNA, Bacterial / Q000032:analysis*; D012260:Ribonucleases; D012261:Ribonucleoproteins / Q000032:analysis*; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D009694:Nucleic Acid Precursors; D009698:Nucleoproteins; D012329:RNA, Bacterial; D012261:Ribonucleoproteins; D012260:Ribonucleases