Ivan Lomakin, PhD

The atomic structures of the small 30S ribosomal subunit from the thermophile bacterium Thermus thermophilus (1) and the large 50S ribosomal subunit from the halophile archaebacterium Haloarcula marismortui (2) provided enormous impact on our understanding of the general mechanism of the protein synthesis. This mechanism is most likely the same between prokaryotic and eukaryotic organisms due to the evolutionary conservation of rRNA and ribosomal proteins. However, eukaryotic rRNA is larger and each ribosomal subunit has more proteins then its prokaryotic counterpart. These structural differences reflect more complicated mechanism of ekaryotic translation. They are especially pronounced at the initiation stage. Translation initiation in eukariotes requires more then 12 protein factors (only 3 in prokaryotes) and utilizes the “cap” structure on the 5’-end of mRNA (3). To start protein synthesis small 40S ribosomal subunit scan 5’- untranslated region of mRNA to find initiation AUG codon – process that is unique for eukaryotic organisms (4). We are using X-ray crystallography to find how these functional differences correlate with structural properties of eukaryotic ribosomes.