STRUCTURE DETERMINATION OF THE RIBOSOMAL RELEASE FACTORS, RF1, RF2 AND RF3

Laurberg1, Martin ; Gustavsson1,J ; Kristensen1,O ; Aberg2,A ; Al-Karadaghi1,S ; Nakamura3,Y ; Liljas1,A

1Department of Molecular Biophysics, Lund University, Sweden
2ASTRA, Göteborg, Sweden
3Department of Tumor Biology, University of Tokyo, Japan

Protein synthesis is carried out at the ribosome in the living organism. Here mRNA is decoded during synthesis of a given protein. At the end of translation the mRNA stop-codons UAA, UAG or UGA signals termination of protein translation.

The ribosomal factors RF1, RF2 and RF3 are directly involved in this step.

RF1 and RF2 are approximately 45 kDa proteins directly involved in the recognition of stop codons. RF1 and RF2 both facilitates termination at the UAA stop codon. Moreover RF1 also catalyses stop at UAG and RF2 catalyses stop at UGA. Upon stop codon recognition, RF1/RF2 triggers hydrolysis of peptidyl-tRNA in the ribosomal P site and thereby releasing the nascent polypeptide chain.

The G-protein RF3 is an approximately 60 kDa protein. It does not recognise stop codons, but it stimulates the effect of RF1 and RF2 in the presence of GTP,,. In yeast, eRF3 (Sup35p) is shown to make a complex with eRF1(Sup45p) in solution.

The poster will present our recent progress towards a crystallographic structure determination of these proteins.

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