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clase de traduccion y codigo genetico
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Traduccin (sntesis de protenas)&
Cdigo Gentico
Jorge Arvalo
2014
Estructura del ribosoma
Figure 27.13: Components of a 70S prokaryotic ribosome.
Figure 27.19: Assembly map for the 30S subunit.
Adapted from A. Spirin, Ribosome Structure and Protein Biosynthesis (Redwood City, Calif.: Benjamin/Cummings, 1986). 1986 Benjamin/Cummings Publishing Company.
Figure 27.16: Low-resolution models of the small and large ribosomal subunits and their 70S complex, as deduced from early electron microscopy studies.
Courtesy of M. Oaks, A. Scheirman, T. Atha, G. Shankweiler, and J. A. Lake, The Ribosome, W. E. Hill, A. Dahlberg, R. A. Garret, P. B. Moore, D. Schlessinger, and J. R. Warner, eds.,p. 181 (New York:American Society of Microbiology Press, 1990).
Figure 27.18: A model of the large ribosomal subunit at 0.9 nm resolution, as determined by x-ray diffraction from crystals.
Provided by N. Ban, P. Nissen, P. Moore, and T. A. Steitz from N. Ban et al., Cell (1998) 93:1105-1115. Cell Press.
Estructura del tRNA
Funcin citoplasmtica del tRNA (aminoacilacin)
Etapas de la traduccin
Figure 27.25: A schematic view of functional regions of the ribosome.
La actividad cataltica peptidil transferasa esta en el 23S rRNA
Regin Peptidil Transferasa conservada
P Nissen et al. Science 2000;289:920-930
Published by AAAS
Mecanismo propuesto de formacion de enlace peptdico por el 23S
rRNA
A proposed mechanism of peptide synthesis catalyzed by the ribosome. A2486 (A2451) is shown as the standard tautomer in all steps, but could be represented as the imino tautomer, which would have a negative unprotonated N3 and a neutral protonated N3. We expect that the electronic distribution is actually between these two extremes. (A) The N3 of A2486 abstracts a proton from the NH2 group as the latter attacks the carbonyl carbon of the peptidyl-tRNA. (B) A protonated N3 stabilizes the tetrahedral carbon intermediate by hydrogen bonding to the oxyanion. (C) The proton is transferred from the N3 to the peptidyl tRNA 3 OH as the newly formed peptide deacylates. Among the variations on this mechanism that should be considered would be a protonated A2486 stabilizing the intermediate, as in (B), with less contribution on acid-base catalysis, as shown in (A) and (C).
Figure 27.28: Some antibiotics that act by interfering with protein biosynthesis.
Inhibe la union de aminoacil-tRNA al ribosoma
Inhibe la actividad peptidil
transferasa del ribosoma
Interfiere la interaccion anticodon-codon.
EL CODIGO GENETICO
El descubrimiento del cdigo gentico
El cdigo gentico es universal
El cdigo gentico es degenerado
El cdigo gentico refleja la existencia de la presin de seleccin
La diversidad de codificacin del genoma es incrementada por las
opciones de franja de lectura
Mutaciones sin sentido (nonsense) y mutantes supresoras
Figure 27.27: How an intergenic suppression mutation can overcome a nonsense mutation.