title: Transit of tRNA through the Escherichia coli ribosome: cross-linking of the 3' end of tRNA to ribosomal proteins at the P and E sites.
abstract: Photoreactive derivatives of yeast tRNA(Phe) containing 2-azidoadenosine at their 3' termini were used to trace the movement of tRNA across the 50S subunit during its transit from the P site to the E site of the 70S ribosome. When bound to the P site of poly(U)-programmed ribosomes, deacylated tRNA(Phe), Phe-tRNA(Phe) and N-acetyl-Phe-tRNA(Phe) probes labeled protein L27 and two main sites within domain V of the 23S RNA. In contrast, deacylated tRNA(Phe) bound to the E site in the presence of poly(U) labeled protein L33 and a single site within domain V of the 23S rRNA. In the absence of poly(U), the deacylated tRNA(Phe) probe also labeled protein L1. Cross-linking experiments with vacant 70S ribosomes revealed that deacylated tRNA enters the P site through the E site, progressively labeling proteins L1, L33 and, finally, L27. In the course of this process, tRNA passes through the intermediate P/E binding state. These findings suggest that the transit of tRNA from the P site to the E site involves the same interactions, but in reverse order. Moreover, our results indicate that the final release of deacylated tRNA from the ribosome is mediated by the F site, for which protein L1 serves as a marker. The results also show that the precise placement of the acceptor end of tRNA on the 50S subunit at the P and E sites is influenced in subtle ways both by the presence of aminoacyl or peptidyl moieties and, more surprisingly, by the environment of the anticodon on the 30S subunit.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA 01003, USA.
authors.forename: Stanislav V
authors.initials: SV
authors.lastname: Kirillov
authors.forename: Jacek
authors.initials: J
authors.lastname: Wower
authors.forename: Stephen S
authors.initials: SS
authors.lastname: Hixson
authors.forename: Robert A
authors.initials: RA
authors.lastname: Zimmermann
mesh_terms: D000215:Acylation; D001665:Binding Sites; D001692:Biological Transport; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D019920:Photoaffinity Labels / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism*; D012360:RNA, Transfer, Phe / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism*
chemical_list: D019920:Photoaffinity Labels; D012360:RNA, Transfer, Phe; D012269:Ribosomal Proteins; D012343:RNA, Transfer