Effect of gamma-aminobutyric acid on cell-free protein synthesizing systems from mouse brain.

GABA stimulates the amino acid incorporating activity of cell-free protein synthesizing systems from mouse brain within a concentration range between 1 muM and 1 mM. This stimulating effect can be measured in systems with free and membrane-bound polysomes as well as in systems with mitochondria or synaptosomes. There is, however, no GABA effect on cell-free systems with polysomes or mitochondria from mouse liver. In the presence of 100 muM GABA aminoacylation of brain tRNA distinctly exceeds the in vitro loading of tRNA in control systems without GABA. Saturating the polysomal systems with precharged [14C]Phe-tRNA results in a loss of GABA stimulation, which is also observed if brain tRNA is charged by pH 5 enzymes from mouse liver. According to these data, GABA seems to have an organ-specific stimulating effect on cell-free systems from mouse brain. In the polysomal systems the site of this GABA effect within the step sequence in protein biosynthesis is the aminoacylation of tRNA and the target of its action seems to be the tRNA itself.