A Cucumis sativus cell-free translation system: preparation, optimization and sensitivity to some antibiotics and ribosome inactivating proteins

A cell-free translation system was prepared from 3- to 5-day-old embryonic axes of gherkin ( Cucumis sativus L.). The system was optimized for Mg²⁺, K⁺, NH⁺₄, high speed supernatants, tRNA mixture from wheat germ, time and temperature. The system translates efficiently both endogenous mRNA (using a 30000 g supernatant) and polyuridylic acid (using either a 30000 g supernatant or a 100000 g supernatant supplemented with purified ribosomes). Translation by gherkin ribosomes was inhibited by several well-known eukaryotic inhibitors, antibiotics and ribosome-inactivating proteins. A translational inhibitory activity found in Cucumis sativus L. dry seeds acted on polypeptide synthesis carried out by cell-free systems from several mammals and plants, including gherkin embryonic axes. Our results indicate that the inhibitor is located in the seed bark and cotyledons, and is either blocked or absent in the embryonic axes, thus allowing the isolation of active gherkin ribosomes. The presence of the putative inhibitor appeared to be unevenly distributed in developing plants.