title: The effect of tRNA binding on the structure of 5 S RNA in Escherichia coli. A chemical modification study.
abstract: The structure of 5 S RNA within the 70 S ribosome from Escherichia coli was studied using the chemical reagent kethoxal (alpha-keto-beta-ethoxybutyraldehyde) to modify accessible guanosines. The modification pattern of 5 S RNA from free 70 S ribosomes was compared with that of poly(U) programmed ribosomes where tRNA had been bound to both the A- and P-sites. Binding to the ribosomal A-site was achieved enzymatically using the elongation factor Tu and GTP in the presence of deacylated tRNA which blocks the ribosomal P-site. Modified guanosines were identified after partial RNase T1 hydrolysis and separation of the hydrolysis products on sequencing gels. Binding of tRNA to the ribosome leads to a strong protection of 5 S RNA guanosine G-41 and to some degree G-44 from kethoxal modification. The limited RNase T1 hydrolysis pattern provides evidence for the existence of a 5 S RNA conformation different from the known 5 S RNA A- and B-forms which are characterized by their gel electrophoretic mobility. The importance of 5 S RNA for the binding of tRNA to the ribosome is discussed.
mesh_terms: D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000032:analysis*; D012343:RNA, Transfer / Q000378:metabolism*; D006163:Ribonuclease T1 / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism
chemical_list: D012329:RNA, Bacterial; D012343:RNA, Transfer; D006163:Ribonuclease T1