Miniaturized hemoproteins: design, synthesis and characterization of mimochrome II

The present paper describes the design, synthesis and spectroscopic characterization of mimochrome II, namely 3,7,12, 17-tetramethylporphyrin-2,18-di-N(9)epsilon-(Ac-Asp(1)-Leu(2)-Ser(3)-Asp(4-)Leu(5)-His(6)-Ser(7)-Lys(8)-Lys(9)-Leu(10)-Lys(11)-Ile(12)-Thr(13)-Leu(14)-NH2) propionamide, and its cobalt derivative. Mimochrome II belongs to a new class of hemoprotein models, called mimochromes. We have developed these molecules in order to investigate the effect of protein structure and composition an modulation of the activity of the heme center. These molecules are composed of two helical peptide chains linked covalently to the deuteroporphyrin IX. The synthetic procedure we developed for synthesizing the prototype molecule mimochrome I, together with the information derived from the structural characterization of the Fe(III)- and Co(III)mimochrome I complexes, enabled us to design molecules having more precise properties. By comparing the behavior of Co(III)-mimochrome II with that of the prototype molecule mimochrome I, we show here that the composition and folding of the peptide chains affect critically the overall structural organization of the models.