The ribosomes of the simian malaria Plasmodium knowlesi—II. A cell-free protein synthesizing system

Abstract

1. 1. Optimal incorporation of radioactive amino acids into protein with the Plasmodium knowlesi (simian malaria) ribosome system required: pH 5 enzymes, magnesium ions and an energy generating system. In the system directed by endogenous messenger the optimum concentration of magnesium was 6–8 mM. 2. 2. Incorporation of radioactive phenylalanine, stimulated by the addition of the synthetic messenger poly(U), was maximal with 10 mM magnesium. 3. 3. Ribosomes isolated from erythrocyte-free plasmodia were a mixed population of polysomes and monosomes with the latter in preponderance; it is suggested that this was due to nuclease activity as well as the nature of the source material. 4. 4. The poly(U)-directed synthesis of polyphenylalanine was inhibited (> 95%) by 1 × 10 −4 M puromycin, cycloheximide, nucleocidin, chlortetracycline, ethidium and berenil; 5 × 10 −4 M emetine was strongly inhibitory. 5. 5. Atebrine, quinine and streptomycin inhibited incorporation by ≈ 50% at a concentration of 5 × 10 −4 M . Proguanil, chloroquine, primaquine, dapsone, cordycepin, mepharside, pyrimethamine and chloramphenicol were without effect.