Journal
NUCLEIC ACIDS RESEARCH
Volume 38, Issue 12, Pages 4108-4119Publisher
OXFORD UNIV PRESS
DOI: 10.1093/nar/gkq151
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Funding
- Ministerio de Educacion y Ciencia (Spain) [BFU 2006-04404]
- National Science Foundation
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Ribotoxins are potent inhibitors of protein biosynthesis and inactivate ribosomes from a variety of organisms. The ribotoxin alpha-sarcin cleaves the large 23S ribosomal RNA (rRNA) at the universally conserved sarcin-ricin loop (SRL) leading to complete inactivation of the ribosome and cellular death. The SRL interacts with translation factors that hydrolyze GTP, and it is important for their binding to the ribosome, but its precise role is not yet understood. We studied the effect of alpha-sarcin on defined steps of translation by the bacterial ribosome. alpha-Sarcin-treated ribosomes showed no defects in mRNA and tRNA binding, peptide-bond formation and sparsonnycin-dependent translocation. Cleavage of SRL slightly affected binding of elongation factor Tu ternary complex (EF-Tu center dot GTP center dot tRNA) to the ribosome. In contrast, the activity of elongation factor G (EF-G) was strongly impaired in alpha-sarcin-treated ribosomes. Importantly, cleavage of SRL inhibited EF-G binding, and consequently GTP hydrolysis and mRNA-tRNA translocation. These results suggest that the SRL is more critical in EF-G than ternary complex binding to the ribosome implicating different requirements in this region of the ribosome during protein elongation.
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