Ribosomal RNA supplementation highly reinforced cell-free translation activity of wheat germ

We have constructed an inexpensive, highly efficient eukaryotic cell-free t ranslation system. Wheat germ rRNA (WG rRNA) was prepared by phenol/chlorof orm (P/C) extraction, a simple and quick method, from wheat germ, an inexpe nsive and commercially available by-product of flour production. Addition o f a small amount of WG rRNA into a wheat germ cell-free translation system increased the protein productivity of the system 6- to 8-fold. Isolated 18S or 285 rRNA alone enhanced the protein production only 2 fold or 3.9-fold, respectively, at maximum. On the other hand, their equimolar mixture enhan ced the production as much as the whole WG rRNA, indicating 18S and 285 rRN A synergistically functioned to enhance protein synthesis. Addition of WG r RNA slightly improved the stability of mRNA in the cell-free translation sy stem, which explained only partly the enhancement of protein production. Ad dition of WGE or ribosome containing approximately the same amount of rRNA in the form of protein-rRNA complex as WG rRNA added to the system did not increase the protein production in the translation system. When ribosome in the cell-free translation system was replaced with WG rRNA, the system did not exhibit any detectable translation activity, indicating that the trans lation activity of WG rRNA is negligible in comparison with that of ribosom e. These results indicated that WG rRNA affected some mechanisms regulating the translation rate in wheat germ cell free system, resulting in increase d protein production.