AN A TO U TRANSVERSION AT POSITION-1067 OF 23-S RIBOSOMAL-RNA FROM ESCHERICHIA-COLI IMPAIRS EF-TU AND EF-G FUNCTION

Escherichia coli ribosomes with an A to U transversion at nucleotide 1 067 of their 23 S rRNA are impaired in their effective association rat e constants (k(cat)/K-M) for both EF-Tu and EF-G binding. In addition, the times that EF-G and EF-Tu spend on the ribosome during elongation are significantly increased by the A to U transversion. The U1067 mut ation impairs EF-Tu function more than EF-G function. The increase in the time that EF-Tu remains bound to ribosome is caused, both by a slo wer rate of GTP-hydrolysis in ternary complex and by a slower EF-Tu.GD P release from the mutated ribosomes. There is, at the same time, no c hange in ribosomal accuracy for aminoacyl-tRNA recognition. With suppo rt from these new data we propose that nucleotide 1067 is part of the ribosomal A-site where it directly interacts with both EF-G and EF-Tu. (C) 1997 Academic Press Limited.