The Binding Site of Escherichia coli Ribosomal Protein S4 on 16-S Ribosomal RNA from Different Bacterial Species

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Abstract
Ribosomal protein S4 of Escherichia coli was bound to 16‐S ribosomal RNAs from several bacterial species and the complexes digested with pancreatic ribonuclease in an effort to isolate heterologous RNA binding sites for protein S4. 16‐S RNAs from Aerornonas punctaia, Pseudomomas fluorescens and Vibrio cuneatus each gave rise to protected fragments whose electrophoretic mobility was 7 S, i.e. similar to that of the fragment generated from E. coli 16‐S RNA using the same conditions. No comparable fragment was obtained from 16‐S RNA of either Bacillus subtilis or Bacillus stearothermophilus, if E. coli protein S4 was present prior to digestion. The protected 7‐S RNA fragment from A. punctata and the subfragments obtained from it by gel electrophoresis under denaturing conditions were characterized further by fingerprinting and nucleotide sequence analysis. The sequence of many of the T1 ribonuclease oligonucleotides was obtained and compared to those from the E. coli 7‐S fragment. This has permitted a tentative identification of the sequences of A. punctata 16‐S RNA which are protected by E. coli protein S4, namely, the regions homologous to the E. coli sequence from section M through C″. The fingerprints of the protected 7‐S fragments from both P. fluorescens and V. cuneatus were sufficiently different from that of the E. coli 7‐S fragment that no conclusions regarding sequence homologies could be drawn.