Volume 6 Number 51979 Nucleic Ac ids Research Initiation of translation with Pseudomonas aeruginosa phage PP7 RNA: nucleotide sequence of the coat cistron ri bo so me binding site

Initiation complex formation between PP7 RNA and ribosomes of Pseudomonas aeruginosa and Escherichia coli has been investigated. The PP7 RNA fragments protected by both species of ribosome have been isolated, and their sequences have been determined. Only one binding site is available on the intact PP7 RNA strand, and this site is recognized by ribosomes of both species. The PP7 RNA binding site is approximately 38 nucleotides long. It contains two AUG sequences and a purine-rich segment near the 5'-end that is complementary to segments near the 3'-ends of the 16S ribosomal RNA's of both P_. aeruginosa and £. coli. In order to establish which of the AUG codons acts as the initiator, the H2N-terminal amino acid sequence of PP7 coat protein was determined. This sequence is compatible with the codon sequence following the second AUG codon. The extent of the reaction of PP7 RNA with E_. coli ribosomes is greater than with P. aeruginosa ribosomes, but our results do not indicate a qualitative difference in the initial interactio