A complex of microperoxidase with a synthetic peptide: structural and functional characterization.

This paper reports the kinetic and thermodynamic characterization of the complex obtained by binding to microperoxidase (the heme-containing undecapeptide derived from peptic hydrolysis of cytochrome c) a 13 residues synthetic peptide with some propensity to acquire alpha-helical secondary structure (P13). Our results indicate that P13 binds to the sixth coordination position of the Fe(III) of microperoxidase (Keq = 4.8 x 10(4) M-1 at pH 7.0 and 25 degrees C) via the imidazole of His-12, forming a stable complex. The kinetics of complex formation, its secondary structure and its electrochemical activity are reported. This is a first step towards engineering a miniature-heme complex, for a better understanding of the mechanisms governing electron transfer in hemes and heme-proteins, and possibly for novel biotechnological applications.