Cell-free protein synthesis directed by coliphage MS2 RNA: Synthesis of intact viral coat protein and other products

Abstract

Coliphage MS2 RNA directs the synthesis in Escherichia coli extracts of a protein product the tryptic peptides of which correspond to the peptides of the phage coat protein. Fingerprint analysis of the synthetic protein labeled with various [14C]amino aeids indicated that in each case only those coat protein peptides which contain a particular amino acid were labeled. The formation of whole coat protein molecules as the predominant product was shown by co-chromatography on Sephadex with authentic phage coat subunit. Sequential synthesis of coat protein ending at the carboxyl end was observed by pulse-labeling with radioactive amino acid and by analysis of the peptides formed in the presence of puromycin. In addition to phage coat protein, MS2 RNA directed the synthesis of other proteins. These could be preferentially labeled with histidine, an amino acid lacking in the coat protein, and partially separated on Sephadex.