[Effects of melittin and its tetraacetyl derivative on rat liver mitochondria]

The uncoupling effect of melittin, the principal peptide of bee venom was studied. It was found that the activation of mitochondrial respiration by melittin and its derivative is due to the formation of channels equally penetrable for lithium, sodium, potassium and rubidium ions. The penetrability of the inner mitochondrial membrane appears at melittin or tetraacetyl melittin concentrations about 0.90 or 0.15 nmol/mg of protein, respectively. The appreciable increase of the uncoupling activity of melittin under blocking of its amino groups suggests that these groups are not very essential for the channel formation. In contrast to gramicidin S and similar to gramicidin A, the effect of melittin develops in time. The lag in the effects of melittin and its derivative indicates that the slow rearrangement stage precedes the formation of channels in the membrane. It is suggested that the effects of melittin are due to the formation of multimolecular complexes of the peptide with phosphatides of the inner mitochondrial membrane.