Modification of Heme Peptides by Reverse Proteolysis:  Spectroscopy of Microperoxidase-10 with C-Terminal Histidine, Tyrosine, and Methionine Residues

Abstract

Small-molecule analogs of the active sites of heme proteins are under investigation in many laboratories. Covalent attachment of ligands to the porphyrins is often desirable as it reduces complications due to axial ligand dissociation and scrambling in cases involving mixed axial ligation. The preparation of ligand-linked (tailed) porphyrin systems, however, often involves complex multistep syntheses. We have found that trypsin-catalyzed reverse proteolysis provides a simple preparative route to a novel class of water-soluble tailed porphyrins based on the well-characterized microperoxidase (MP) framework. Using reverse proteolysis reactions, we have obtained mutant microperoxidase decapeptides (MP10s) with C-terminal histidine (H23MP10), tyrosine (Y23MP10), and methionine (M23MP10) residues. In addition, we have investigated the electronic absorption and resonance Raman spectra of these MP10 mutants.