Evidence that protein synthesized in a heterologous cell-free system is not functional

Abstract

Recent reports have described synthesis of proteins by Escherichia coli ribosomes in a cell-free system when ribosomal or “messenger” ribonucleic acid (RNA) is supplied ( Nirenberg and Matthei, 1961; Ofengand and Haselkorn, 1962). It has been claimed that the genetic code for protein synthesis carried by the “messenger” RNA is universal and, when supplied with this information, a ribosomal system can synthesize any protein. The criterion for protein synthesis in these experiments was incorporation of labeled amino acids into the acid-precipitated proteins. We have planned the following experiments to determine if a functional protein could be synthesized in such a system, and if this could be accomplished in a heterologous system. Ribosomal RNA from E . coli cells induced to form β-galactosidase was used in E . coli (homologous) and Pseudomonas pyocyaneus (heterologous) cell-free systems. The results are reported in this paper.