Protein Synthesis by a Cell‐Free Preparation from the Bird Malaria, Plasmodium lophurae*

Abstract

Cytoplasmic polyribosomes were isolated from the avian malaria parasite Plasmodium lophurae by lysis with 0.15% Triton X-100 followed by high speed centrifugation through a discontinuous sucrose gradient. Polyribosomes were protected from nuclease degradation using 100 mug/ml heparin or 50 mug/ml dextran sulfate. Cell-free incorporation of radioisotope-labeled amino acids required a pH 5 fraction (duck reticulocyte), Mg2+, and an energy-generating system. The protein synthesizing system was stimulated by the addition of polyuridylic acid. Optimum conditions for protein synthesis by the plasmodial system are described. The effects of drugs on the cell-free protein synthesizing system using duck reticulocyte and plasmodial ribosomes are reported.