Requirement for homologous rabbit reticulocyte initiation factor 3 for initiation of alpha- and beta-globin mRNA translation in a crude protozoal cell-free system.

摘要: Experimental evidence showing specificity of rabbit reticulocyte initiation factor 3 (EIF-3) for selective mRNA translation is presented. A new cell-free system was developed from Crithidia fasciculata. The crude postmitochondrial supernatant fluid treated with puromycin and 0.5 M KCl to dissociate polysomes ribosomes into subunits. drug salt were removed by gel filtration on Sephadex G-25. Additions amino acids energy source initiate protein synthesis. All synthesis starts at the site. This treatment brought about a shift in MgCl2 optimum 6 mM. Exogenously supplied globin faithfully translated this system. However, crithidial EIF-3 has low affinity as evidenced 6-fold increase rate after addition range which linear amount added It also shown that reconstituted ribosomal subunits are depleted factors, reticulocytes higher mRNA, measured formation during time acid incorporation. These results taken indicate action should be considered an enzyme catalyzed reaction various mRNAs serve different substrate analogs. Therefore, most likely expressed would show difference rather than all-or-none phenomenon.