Purification of 70S Ribosomes from Bacillus subtilis

Abstract

The eubacterial ribosome (70S) is a macromolecular complex that is composed of a small (30S) subunit and a large (50S) subunit. The small subunit comprises the 16S ribosomal RNA (rRNA) and more than 20 ribosomal proteins (r-proteins), whereas the large subunit comprises the 23S and 5S rRNAs and more than 30 r-proteins. Bacillus subtilis (B. subtilis) has 57 r-ribosomal protein genes and three rRNAs (16S, 23S and 5S rRNAs). Among them, we identified 21 r-proteins of the small subunit and 31 r-proteins of the large subunit in B. subtilis (Nanamiya et al., 2004). The functions and roles of individual components of the ribosome have not yet been completely clarified. Herein we describe in detail an ultracentrifugation-based protocol for the preparation of 70S ribosomes from exponentially growing cells of B. subtilis.