CRYSTALLOGRAPHIC STRUCTURES OF RIBOSOMAL PROTEINS AND ELONGATION FACTOR G. Anders Liljas¹, Maria Garber², Arnthor Avarsson¹, Salam Al-Karadaghi¹, Natalia Davidova², Irina Eliseikina², Natalia Fomenkova², Olga Gryaznova², Natalia Nevskaya², Stanislav Nikonov², Alexey Nikulin², Johan Unge¹, Julia Zheltonosova², ¹Molecular Biophysics, Chemical Center, University of Lund, Box 124, S-221 00 Lund, Sweden; ²Department of Structure and Function of the Ribosome, Institute of Protein Research, Russian Academy of Sciences, 142292 Pushchino, Moscow Region, Russia

The crystallographic structures of a number of ribosomal proteins have been determined, most recently L1 and L22. A majority of the ribosomal proteins have the split b-a-b fold also observed in RNA/DNA binding proteins. L1 has two domains. The first domain contains both the N- and the C-terminus and has the split b-a-b fold. The topology of the second domain is a minimal version of the "Rossmann fold" with only four parallel b-strands.

The structure of elongation factor G has a remarkable similarity to the ternary complex of EF-Tu.GTP-tRNA with direct implications for the function of EF-G. The observation that ribosomal proteins have similarities to each other and to other RNA binding proteins is also valid for EF-G where domains IV, V and possibly also III have structures similar to ribosomal proteins. The N-terminal domains G and II seem to be present in all ribosome binding GTPases. They probably constitute part of the surface that interacts with a region on the ribosome to which all those factors bind. The conformational changes of the protein are of significant functional relevance. They are found not only in the switch region, but also in neighbouring parts of the structure such as the C helix of the G-domain at the interface between different domains. Mutations of this region with interesting phenotypes have been found not only for EF-G but also in EF-Tu.