Differential effect of Ca +2 on the translation of yeast mitochondrial and some viral RNA's in an [formula omitted] cell-free system

Abstract

Addition of 6mM CaCl 2 to an E. coli cell-free system resulted in a several-fold enhancement of yeast mt RNA translation and in a severe inhibition of protein synthesis directed by MS2, Qβ and T 5 RNA's. CaCl 2 did not alter the Mg +2 optimum or the time-course of protein synthesis and had no apparent effect on RNA degradation. Formaldehyde treatment of MS2 RNA markedly diminished the CaCl 2-mediated inhibition of its translation. Addition of equimolar amounts of EGTA, together with CaCl 2, abolished the effect of the latter on cell-free protein synthesis. FMet tRNA binding to ribosomes was enhanced by CaCl 2 in the presence of mt RNA, inhibited in the presence of MS2 RNA, and unaffected in the presence of formaldehyde-treated MS2 RNA. Maximal effect on initiation complex formation was observed with 0.1 mM CaCl 2.