The Interaction of Melittin with Calmodulin and Its Tryptic Fragments

Melittin has been found to interact with both the N- and C-terminal half-molecules of calmodulin, as well as the intact molecule, in the presence of Ca2+. The interaction results in a major change in the microenvironment of Trp-19, which is in a more nonpolar, solvent-shielded, and immobilized microenvironment in the complex. The properties of Tyr-99 and Tyr-138 of calmodulin are altered by complex formation. From measurements of the efficiencies of radiationless energy transfer from Trp-19 to the nitro derivatives of Tyr-99 and/or Tyr-138, it is concluded that Trp-19 is located in proximity to the C-terminal lobe of calmodulin in the complex.