Effect of point mutations at position 89 of the E. coli 5S rRNA on the assembly and activity of the large ribosomal subunit.

Nucleotide residue U89 in the D loop of Escherichia coli 5S rRNA is adjacent to two domains of 23S rRNA in the large ribosomal subunit [Dokudovskaya et al., RNA 2 (1996) 146-152]. 50S ribosomal subunits were reconstituted containing U89(C, G or A) mutants of 5S rRNAs and the activities of the corresponding 70S ribosomes were studied. The U89C mutant behaves similarly to the wild-type 5S rRNA. Replacement of the pyrimidine base at position U89 by more bulky purine bases impairs the incorporation of 5S rRNA into 50S subunits, whereas the particles formed showed full activities in poly(U)-dependent poly(Phe) synthesis in the presence of either U89G or U89A 5S rRNA mutants. The activity of the reconstituted particles depends on the incorporation of 5S rRNA in agreement with early observations.