Activation of translationally inactive lipoxygenase mRNP particles from rabbit reticulocytes.

The free cytoplasmic mRNP fraction of rabbit reticulocytes consists mainly of globin mRNP particles but contains substantial amounts of lipoxygenase mRNPs. mRNPs were isolated by affinity chromatography on oligo(dT)cellulose. The lipoxygenase specific mRNPs are in size between 30 and 80 S in sucrose density gradients as judged by Northern blot analysis with a specific lipoxygenase-plasmid probe and are translationally inactive in cell-free protein synthesis. Inhibition of lipoxygenase mRNP translation can be abolished by treatment of the particles with 0.65-0.8 M KCI which leads to a dissociation of masking proteins. Lipoxygenase mRNPs prepared from young reticulocytes can be activated in vitro by incubation with cytoplasm of more mature reticulocytes but not with cytoplasm of erythrocytes. Preliminary experiments indicate that Ca2+ ions may be involved in lipoxygenase mRNP activation.