Patricia Julián

Publications (2)21.13 Total impact

• Source

  Available from: Gorka Lasso

  Article: The Cryo-EM structure of a complete 30S translation initiation complex from Escherichia coli.

  Patricia Julián, Pohl Milon, Xabier Agirrezabala, Gorka Lasso, David Gil, Marina V Rodnina, Mikel Valle
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  ABSTRACT: Formation of the 30S initiation complex (30S IC) is an important checkpoint in regulation of gene expression. The selection of mRNA, correct start codon, and the initiator fMet-tRNA(fMet) requires the presence of three initiation factors (IF1, IF2, IF3) of which IF3 and IF1 control the fidelity of the process, while IF2 recruits fMet-tRNA(fMet). Here we present a cryo-EM reconstruction of the complete 30S IC, containing mRNA, fMet-tRNA(fMet), IF1, IF2, and IF3. In the 30S IC, IF2 contacts IF1, the 30S subunit shoulder, and the CCA end of fMet-tRNA(fMet), which occupies a novel P/I position (P/I1). The N-terminal domain of IF3 contacts the tRNA, whereas the C-terminal domain is bound to the platform of the 30S subunit. Binding of initiation factors and fMet-tRNA(fMet) induces a rotation of the head relative to the body of the 30S subunit, which is likely to prevail through 50S subunit joining until GTP hydrolysis and dissociation of IF2 take place. The structure provides insights into the mechanism of mRNA selection during translation initiation.
  PLoS Biology 07/2011; 9(7):e1001095. · 11.45 Impact Factor
• Source

  Available from: David Gil-Carton

  Article: Structure of ratcheted ribosomes with tRNAs in hybrid states.

  Patricia Julián, Andrey L Konevega, Sjors H W Scheres, Melisa Lázaro, David Gil, Wolfgang Wintermeyer, Marina V Rodnina, Mikel Valle
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  ABSTRACT: During protein synthesis, tRNAs and mRNA move through the ribosome between aminoacyl (A), peptidyl (P), and exit (E) sites of the ribosome in a process called translocation. Translocation is accompanied by the displacement of the tRNAs on the large ribosomal subunit toward the hybrid A/P and P/E states and by a rotational movement (ratchet) of the ribosomal subunits relative to one another. So far, the structure of the ratcheted state has been observed only when translation factors were bound to the ribosome. Using cryo-electron microscopy and classification, we show here that ribosomes can spontaneously adopt a ratcheted conformation with tRNAs in their hybrid states. The peptidyl-tRNA molecule in the A/P state, which is visualized here, is not distorted compared with the A/A state except for slight adjustments of its acceptor end, suggesting that the displacement of the A-site tRNA on the 50S subunit is passive and is induced by the 30S subunit rotation. Simultaneous subunit ratchet and formation of the tRNA hybrid states precede and may promote the subsequent rapid and coordinated tRNA translocation on the 30S subunit catalyzed by elongation factor G.
  Proceedings of the National Academy of Sciences 12/2008; 105(44):16924-7. · 9.68 Impact Factor