Interaction between eukaryotic initiation factors 1A and 5B is required for efficient ribosomal subunit joining.

Acker, Michael G; Shin, Byung-Sik; Dever, Thomas E; Lorsch, Jon R

Acker, Michael G; Shin, Byung-Sik; Dever, Thomas E; Lorsch, Jon R.

Afiliación

Acker MG; Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

J Biol Chem ; 281(13): 8469-75, 2006 Mar 31.

Article en En | MEDLINE | ID: mdl-16461768

RESUMEN

Eukaryotic initiation factor 5B (eIF5B) is a GTPase that facilitates joining of the 60 S ribosomal subunit to the 40 S ribosomal subunit during translation initiation. Formation of the resulting 80 S initiation complex triggers eIF5B to hydrolyze its bound GTP, reducing the affinity of the factor for the complex and allowing it to dissociate. Here we present a kinetic analysis of GTP hydrolysis by eIF5B in the context of the translation initiation pathway. Our data indicate that stimulation of GTP hydrolysis by eIF5B requires the completion of early steps in translation initiation, including the eIF1- and eIF1A-dependent delivery of initiator methionyl-tRNA to the 40 S ribosomal subunit and subsequent GTP hydrolysis by eIF2. Full activation of GTP hydrolysis by eIF5B requires the extreme C terminus of eIF1A, which has previously been shown to interact with the C terminus of eIF5B. Disruption of either isoleucine residue in the eIF1A C-terminal sequence DIDDI reduces the rate constant for GTP hydrolysis by approximately 20-fold, whereas changing the aspartic acid residues has no effect. Changing the isoleucines in the C terminus of eIF1A also disrupts the ability of eIF5B to facilitate subunit joining. These data indicate that the interaction of the C terminus of eIF1A with eIF5B promotes ribosomal subunit joining and possibly provides a checkpoint for correct complex formation, allowing full activation of GTP hydrolysis only upon formation of a properly organized 80 S initiation complex.

Asunto(s)

Factor 1 Eucariótico de Iniciación/metabolismo; Factores Eucarióticos de Iniciación/metabolismo; Iniciación de la Cadena Peptídica Traduccional; Ribosomas/metabolismo; Secuencia de Aminoácidos; Sustitución de Aminoácidos; Escherichia coli/genética; Factor 1 Eucariótico de Iniciación/química; Factor 1 Eucariótico de Iniciación/genética; Factor 1 Eucariótico de Iniciación/aislamiento & purificación; Factores Eucarióticos de Iniciación/química; Factores Eucarióticos de Iniciación/genética; Factores Eucarióticos de Iniciación/aislamiento & purificación; Polarización de Fluorescencia; GTP Fosfohidrolasas/análisis; GTP Fosfohidrolasas/metabolismo; Guanosina Trifosfato/metabolismo; Histidina/química; Hidrólisis; Isoleucina/metabolismo; Cinética; Metionina/metabolismo; Modelos Biológicos; Radioisótopos de Fósforo; Estructura Terciaria de Proteína; ARN Mensajero/metabolismo; ARN de Transferencia/metabolismo; Saccharomyces cerevisiae/genética; Saccharomyces cerevisiae/metabolismo; Radioisótopos de Azufre

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Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Iniciación de la Cadena Peptídica Traduccional / Ribosomas / Factor 1 Eucariótico de Iniciación / Factores Eucarióticos de Iniciación Tipo de estudio: Prognostic_studies Idioma: En Revista: J Biol Chem Año: 2006 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos

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