Replacement of the L11 binding region within E.coli 23S ribosomal RNA with its homologue from yeast: in vivo and in vitro analysis of hybrid ribosomes altered in the GTPase centre.
Replacement of the protein L11 binding domain within Escherichia coli 23S ribosomal RNA (rRNA) by the equivalent region from yeast 26S rRNA appeared to have no effect on the growth rate of E.coli cells harbouring a plasmid carrying the mutated rrnB operon. The hybrid rRNA was correctly processed and assembled into ribosomes, which accumulated normally in polyribosomes. Of the total ribosomal population, < 25% contained wild-type, chromosomally encoded rRNA; the remainder were mutant. The hybrid ribosomes supported GTP hydrolysis dependent upon E.coli elongation factor G, although at a somewhat reduced rate compared with wild-type particles, and were sensitive to the antibiotic, thiostrepton, a potent inhibitor of ribosomal GTPase activity that binds to 23S rRNA within the L11 binding domain. That thiostrepton could indeed bind to the mutant ribosomes, although at a reduced level relative to that seen with wild-type ribosomes, was confirmed in a non-equilibrium assay. The rationale for the ability of the hybrid ribosomes to bind the antibiotic, given that yeast ribosomes do not, was provided when yeast rRNA was shown by equilibrium dialysis to bind thiostrepton only 10-fold less tightly than did E.coli rRNA. The extreme conservation of secondary, but not primary, structure in this region between E.coli and yeast rRNAs allows the hybrid ribosomes to function competently in protein synthesis and also preserves the interaction with thiostrepton.
Thompson
J
J
Department of Biochemistry, University of Leicester, UK.
Musters
W
W
Cundliffe
E
E
Dahlberg
A E
AE
D001483:Base Sequence; D001665:Binding Sites; D004252:DNA Mutational Analysis; D020963:GTP Phosphohydrolase-Linked Elongation Factors / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors / Q000378:metabolism; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics; D012331:RNA, Fungal / Q000737:chemistry / Q000235:genetics; D012338:RNA, Ribosomal, 23S / Q000737:chemistry* / Q000648:ultrastructure; D012269:Ribosomal Proteins / Q000378:metabolism*; D012270:Ribosomes / Q000378:metabolism / Q000648:ultrastructure*; D013329:Structure-Activity Relationship; D013883:Thiostrepton / Q000378:metabolism
D020653:Peptide Elongation Factor G; D010445:Peptide Elongation Factors; D012329:RNA, Bacterial; D012331:RNA, Fungal; D012338:RNA, Ribosomal, 23S; D012269:Ribosomal Proteins; C027624:ribosomal protein L11; D006160:Guanosine Triphosphate; D020963:GTP Phosphohydrolase-Linked Elongation Factors; D013883:Thiostrepton