Translation of virus mRNA: Synthesis of bacteriophage PP7 proteins in cell-free extracts from Pseudomonas aeruginosa

Abstract

The translation of Pseudomonas phage PP7 RNA has been investigated, using cell-free extracts from Pseudomonas aeruginosa, strain 1. S-30 extracts translated PP7 phage RNA quite efficiently, but the isolated ribosomes incubated with an Escherchia coli S-100 supernatant preparation, were even more active. Three distinct products are made which correspond to in vivo labeled PP7 phage polypeptides judged by polyacrylamide-SDS gels. It is suggested that the PP7 genome has at least three cistrons. The major product of in vitro synthesis, synthesized in great excess of the other products, coelectrophoreses with authentic coat protein prepared from labeled phage. Tryptic peptide analysis of this product yielded leucine labeled tryptic peptides very similar to those of PP7 coat protein. It is concluded that this in vitro polypeptide is the product of the coat protein cistron. This product was also efficiently synthesized when PP7 RNA was translated by E. coli ribosomes, but the other PP7 genome products are not made, except occasionally in very small amounts. This result, and the fact that Pseudomonas ribosomes translate PP7 RNA more efficiently than R17 and Qβ RNA, indicates differential cistron recognition between Pseudomonas and E. coli ribosomes or their initiation factors.