NATURE OF THE AMINO-ACID POOL USED FOR PROTEIN-SYNTHESIS IN RAT-BRAIN SLICES

The incorporation into brain slice protein of externally provided [1‐14C]valine was measured at varying levels of valine in the medium, under conditions of constant protein synthesis and equilibration of intracellular valine specific activity. The results indicate that the valine pool used for protein synthesis is not identical to the pool of total free valine. Neither does the incorporation solely occur from an extracellular pool which is in equilibrium with the incubation medium. The data are compatible with a two‐site activation model in which aminoacylation of tRNA occurs at both an internal site utilizing amino acid from the intracellular pool and an external (possibly membranous) site converting extracellular valine directly to valyl‐tRNA. A good fit to the experimental observations is also provided by a compartmented intracellular valine pool model. Copyright © 1979, Wiley Blackwell. All rights reserved