Crystal structures of ribosome anti-association factor IF6

Ribosome anti-association factor elF6 (originally named according to transl ation initiation terminology as eukaryotic initiation factor 6) binds to th e large ribosomal subunit, thereby preventing inappropriate interactions wi th the small subunit during initiation of protein synthesis. We have determ ined the X-ray structures of two IF6 homologs, Methanococcus jannaschii arc haeal alF6 and Sacchromyces cerevisiae elF6, revealing a phylogenetically c onserved 25 kDa protein consisting of five quasi identical alpha/beta subdo mains arrayed about a five-fold axis of pseudosymmetry. Yeast elF6 prevents ribosomal subunit association. Comparative protein structure modeling with other known archaeal and eukaryotic homologs demonstrated the presence of two conserved surface regions, one or both of which may bind the large ribo somal subunit.