Interaction of Escherichia coli ribosomal protein S7 with 16S rRNA

The interaction between Escherichia coli ribosomal protein S7 and 16S rRNA was investigated using in vitro synthesized RNA transcripts. It was shown by nitrocellulose membrane filtration that RNA transcripts corresponding to the 3' major domain (nucleotides 926-1393) and to the lower half of this domain (nucleotides 926-986/1219-1393) bound S7 with the same affinity as 16S rRNA. A series of deletion mutants of the DNA coding for the lower half of the 3' major domain were constructed and the corresponding RNA fragments were assayed for their capacity to bind S7. A minimal domain of 108 nucleotides which can still efficiently bind S7 was thus obtained. In this domain, the 1304-1308/1329-1333 irregular helix and the 1351-1371 irregular hairpin were found to contain important determinants for S7 binding.