Aarhus Universitets segl

Crystal Structure of Yeast Elongation Factor 3

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Christian Brix Folsted Andersen - Foredragsholder

  • Molekylærbiologisk Institut

The fungal translation elongation machinery differs from other eukaryotes by requiring a third component: elongation factor 3 (eEF3). eEF3 is essential in vivo and required for each translation elongation cycle in vitro. A proposed function of eEF3 is to facilitate deacylated tRNA release from the ribosomal E-site and promote cognate aminoacyl-tRNA binding to the A-site. Sequence analysis has classified eEF3 as a member of the ATP-Binding Cassette (ABC) superfamily. Other members of this superfamily are ABC50 and GCN20, and the N-terminal of eEF3 is also homologous to a central part of GCN1. These three factors are also involved in translation. We have determined the structure of a slightly truncated form of eEF3 (residues 1-980) to 2.4 Å resolution. The truncated eEF3 was expressed in Saccharomyces cerevisiae as the only form of eEF3 and it is consequently physiologically relevant. It consists of four domains, an N-terminal helical domain with HEAT-repeats, a four-helix bundle and two ABC cassettes. The N-terminal domain is composed of 15 helices forming an elongated curved structure. The two ABC cassettes reveal a fold very similar to that of other ABC cassettes. However, the C-terminal ABC2 contains a 100-amino-acid insert possibly involved in tRNA binding. This insert is structurally homologous to chromo domains. The protein was crystallized in complex with ADP, but no nucleotide is bound at the canonical sites in either ABC1 or ABC2. One ADP molecule binds instead to an unexpected site close to the ABC2 site at the N-terminal domain interface. The relative orientation of ABC1 to ABC2 differs from the ATP binding dimer of ABC cassettes observed in other ABC structures including BtuCD and Rad50. A very large conformational change in eEF3 must be expected upon activation.

9 sep. 2004

Begivenhed (Konference)

TitelTranslational Control
ByCold Spring Harbor Laboratory, Cold Spring Harbor, New York

ID: 3642551