Translational specificity of Bacillus stearothermophilus ribosomes

The translational specificity of Bacillus stearothermophilus ribosomes was studied by determining the effectiveness of various synthetic RNAs as templates at 37 degrees and at higher temperatures. The effectiveness of poly(G,U) was maximal at a G:U ratio of 1:3; it declined with lower G content because of reduced ribosomal affinity for the RNA and, with higher G, because of interference by secondary structure. The effectiveness of poly(A,C,G,U) also declined when secondary structure was increased by increasing (G+C) content. Escherichia coli ribosomes exhibited a similar specificity for poly-(G,U), but had a lower sensitivity to interference by RNA secondary structure. In both bacterial species, sensitivity to secondary structure was determined by the 30S ribosomal subunit.