The dependence of mitochondrial protein synthesis initiation upon the formylation of initiator met-tRNA was investigated in experiments in which the rate of formyl-methionyl-peptidyl-puromycin derivatives formation was measured in the presence or absenceof the appropriate formylating agent. The presence on N10-formyl-THFA increases several times the amount of 14C-Met incorporation in the initial peptides: in addition, when N10-14C-formyl-THFA was supplied, a remarkable amount of radioactivity was recovered bound to N-terminal methionine. Other experiments in which the deformylating activity on formyl-peptides was measured, allowed the conclusion that formyl group and methionine are incorporated in stoichiometric amounts. Thus, the formylation of the initiator met-tRNA is anabsolute requirement for the peptide chain initiation in mitochondria. The biological significance of this requirement is discussed.
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Con il contributo del Ministero per i Beni e le Attività Culturali