1 research outputs found
Influence of the Interdomain Interface on Structural and Redox Properties of Multiheme Proteins
Multiheme
proteins are important in energy conversion and biogeochemical
cycles of nitrogen and sulfur. A diheme cytochrome c4 (c4) was used as a model
to elucidate roles of the interdomain interface on properties of iron
centers in its hemes A and B. Isolated monoheme domains c4-A and c4-B, together with
the full-length diheme c4 and its Met-to-His
ligand variants, were characterized by a variety of spectroscopic
and stability measurements. In both isolated domains, the heme iron
is Met/His-ligated at pH 5.0, as in the full-length c4, but becomes His/His-ligated in c4-B at higher pH. Intradomain contacts in c4-A are minimally affected by the separation of c4-A and c4-B domains,
and isolated c4-A is folded. In contrast,
the isolated c4-B is partially unfolded,
and the interface with c4-A guides folding
of this domain. The c4-A and c4-B domains have the propensity to interact even without
the polypeptide linker. Thermodynamic cycles have revealed properties
of monomeric folded isolated domains, suggesting that ferrous (FeII), but not ferric (FeIII) c4-A and c4-B, is stabilized by
the interface. This study illustrates the effects of the interface
on tuning structural and redox properties of multiheme proteins and
enriches our understanding of redox-dependent complexation