Figure 3. Structural elucidation of heme-binding peptides (classes I–VIII) using 2D-NMR spectroscopy.

Different binding modes occurred depending on the peptide sequence composition and the formation of penta-coordinated (III, IV, V, and VII) and hexa-coordinated complexes (I, II, VI, and VIII). The latter ones emerged in different forms: a sandwich-like complex including two peptides interacting with one heme molecule (I and VIII) and a loop/clamp-like complex for peptides that exhibit additional coordination sites (II and VI) [32,33].