Sedimentation properties of preformed messenger particles in dry rye embryo extracts

Two classes of messenger containing particles can be distinguished in cell-free extracts from dry rye (Secale cereale, L.; var. Celestijner) embryos. A part of the endogenous template activity is associated with large structures, even during in vitro translation. Treatment with detergents results in a partial solubilization of the messenger particles from the large, presumably membranous structures. The sedimentation behavior of the "soluble" mRNP particles (about 75% of the total endogenous template activity) is strongly influenced by the composition of the homogenization medium. At high Mg(2+) or Ca(2+) concentrations, and at low pH, the soluble mRNP particles form aggregates sedimenting at low centrifugal forces. This peculiar behavior is of partical interest with respect to the preparation of cell-free extracts with low endogenous template activity.