Isolation of a translation-inhibiting peptide from myocardium

We previously reported that an initial response to acute cardiac stress is temporary translational inhibition. Using an in vitro translational assay to follow activity, we purified a translation-inhibiting peptide (TIP) obtained from control canine hearts and hearts acutely stressed by ascending aortic banding and heat shock for 1 h. We isolated a 17-kDa peptide. The amino acid composition was determined and residues 3-20 were sequenced. Treatment of polysome preparations with TIP shifted the polysome distribution profile to that characteristic of the acutely stressed heart in which monosomes predominate. Translational inhibition acted by suppressing formation of the 80S initiation complex. Suppression curves indicate that translation is inhibited by approximately 60%, with the translation of protein over 30 kDa being highly suppressed. We postulate that translational inhibition is an essential initial reaction to acute stress that allows the cell to redirect energy into vita cell functions that permit long-term adaptation to the stress. We believe that translational inhibition is effected by intracellular activator of TIP.