RNA sequences associated with proteins L1, L9, and L5, L18, L25, in ribonucleoprotein fragments isolated from the 50-S subunit of Escherichia coli ribosomes.

32P-labelled 50-S subunits from Escherichia coli ribosomes were hydrolysed under conditions known to give rise to two specific ribonucleoprotein fragments, containing proteins L1, L9, and L5, L18 and L25 respectively. RNA corresponding to these ribonucleoproteins was isolated and purified, and the various RNA fragments obtained were subjected to oligonucleotide analysis. The results showed that the RNA associated with proteins L1 and L9 was very similar to the RNA found with protein L1 after controlled digestion of 23-S-RNA - L1 complexes (described elsewhere); this RNA lies within a region 550-1000 nucleotides from the 3' terminus of 23-S RNA. The RNA associated with proteins L5, L18, and L25 consisted predominantly of two species of similar size. One was 5-S RNA, and the other a fragment of 23S RNA, lying within the region 450-1000 nucleotides from the 3' terminus.