The Evolution of Ribosomal Proteins and Yeast

Introduction: We have been interested in analyzing sequence similarities of ribosomal proteins from various organisms from the view point of biological evolution, focusing on yeast. Ribosomes contain many protein species. In the well-studied E. coli, 54 ribosomal proteins (21 in the small subunit and 33 in the large subunit) are known with few others believed to exist (Wada and Sako, 1987). According to the analysis of sequence similarities, some of them have their equivalents in organisms from all three primary kingdoms: eukaryotes, metabacteria and prokaryotes, including the organelles like chloroplasts and mitochondria. It is estimated that some have their equivalents only in prokaryotes, and the others in prokaryotes and metabacteria and/or in prokaryotes and eukaryotes. Similar situations are also seen for ribosomal proteins in eukaryotic and metabacterial species (Fig. 1).