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Abstract: Ribose-5-phosphate isomerase A has an important role in sugar metabolism by interconverting ribose-5-phosphate and ribulose-5-phosphate. This enzyme is ubiquitous and highly conserved among the three kingdoms of life. We have solved the 2.1 Å resolution crystal structure of the Saccharomyces cerevisiae enzyme by molecular replacement. This protein adopts the same fold as its archaeal and bacterial orthologs with two α/β domains tightly packed together. Mapping of conserved residues at the surface of the protein reveals strong invariability of the active site pocket, suggesting a common ligand binding mode and a similar catalytic mechanism. The yeast enzyme associates as a homotetramer similarly to the archaeal protein. The effect of an inactivating mutation (Arg189 to Lys) is discussed in view of the information brought by this structure. [Copyright &y& Elsevier]

During protein synthesis, release of polypeptide from the ribosome occurs when an in frame termination codon is encountered. Contrary to sense codons, which are decoded by tRNAs, stop codons present in the A-site are recognized by proteins named class I release factors, leading to the release of newly synthesized proteins. Structures of these factors bound to termination ribosomal complexes have recently been obtained, and lead to a better understanding of stop codon recognition and its coordination with peptidyl-tRNA hydrolysis in bacteria. Release factors contain a universally conserved GGQ motif which interacts with the peptidyl-transferase centre to allow peptide release. The Gln side chain from this motif is methylated, a feature conserved from bacteria to man, suggesting an important biological role. However, methylation is catalysed by completely unrelated enzymes. The function of this motif and its post-translational modification will be discussed in the context of recent structural and functional studies., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

We present here the outlines and results from our yeast structural genomics (YSG) pilot-project. A lab-scale platform for the systematic production and structure determination is presented. In order to validate this approach, 250 non-membrane proteins of unknown structure were targeted. Strategies and final statistics are evaluated. We finally discuss the opportunity of structural genomics programs to contribute to functional biochemical annotation.