The binding site of protein L1 ON 23-S ribosomal RNA of Escherichia coli. 2. Identification of the rna region contained in the L1 ribonucleoproteins and determination of the order of the RNA subfragments within this region.

Ribonucleoproteins were obtained by T1 ribonuclease digestion of reconstitued complexes of ribosomal protein L1 AND 23-S RNA from Escherichia coli. The RNA region of the main ribonucleoprotein 2 was totally digested with T1 ribonuclease. The oligonucleotide products were characterised and they showed that this region comprises 148 nucleotides located between the 550th and 1000th necleotides from the 3' end of the 23-S RNA. Of the other two ribonucleoproteins, the largest ribonucleoprotein 1 contained an extra RNA sequence, of at least 15 nucleotides, that was located at the 5' end of the RNA region. The smallest ribonucleoprotein 3 lacked an RNA section towards the 3' end of the region. The order of the RNA subfragments and the enzymic cutting positions in the whole RNA region are given for the ribonucleoproteins. It is shown that protein L1 most strongly protects a continuous section of 115 nucleotides at the 5' end of the main RNA region. Finally, evidence is presented for a methylated base, and for two sequence heterogeneities, in this region of the 23-S RNA.