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Multiheme cytochromes c constitutes a widespread class of proteins with essential functions in electron
transfer and enzymatic catalysis. Their functional properties are in part determined by the relative
arrangement of multiple heme cofactors. Understanding the significance of these motifs is crucial for the
elucidation of the highly optimized properties of multiheme cytochromes c, but their spectroscopic
investigation is often restricted by the presence of a large number and efficient coupling of the individual
centers. The diheme cytochrome c (DHC2) from G. sulfurreducens is, however, the simplest member of
such family, with two heme groups attached through a single polypeptide chain that are found to be
different. The observed differences in the axial ligand orientations and porphyrin ring deformations
between two heme centers in DHC2 have been proposed to be the consequences of heme-heme interactions
although the functional significance of these heme structural arrangements is yet to be understood. These
attractive features have prompted us to investigate the relationship between such interactions and the
properties of the metal center as a part of our ongoing research. This talk will highlights some of our recent
results. |