Cell‐Free Protein Synthesis by Rumen Protozoa

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Abstract
SYNOPSIS. The characteristics of protein synthesis by cell‐free extracts of mixed rumen protozoa have been investigated. ATP,1 GTP, and an energy supply system were necessary for amino acid incorporation which was partially inhibited by cycloheximide but not by chloramphenicol (100 μg/ml). The system was particularly sensitive to the cation concentration of the incubation mixture, maximal incorporation requiring 5 mM Mg++ and 50 mM K+ Incorporation was further stimulated by the addition of 0.25 mM spermidine or 0.25 mM MnCl2. Sucrose gradient centrifugation of the cell sap after amino add incorporation showed that most of the incorporated radioactivity was associated with free polysomes. These polysomes contained 82 S ribosomes which dissociated in high Tris concentrations to yield 40 S and 55 S ribosomes.