Structure of Rhodoferax fermentans high-potential iron–sulfur protein solved by MAD

The crystal structure of Rhodoferax fermentans high-potential iron protein (HiPIP) has been solved by MAD methods using the anomalous signal from the Fe atoms in the [Fe₄S₄] cluster present in the protein and refined to a resolution of 1.45 Å. The peptide chain is well defined except in the N- and C-­terminal areas. The structure of the protein reveals the presence of three helical fragments, a small β-sheet and several turns, with the [Fe₄S₄] cluster being located close to a surface patch containing several well conserved aromatic residues. The protein fold is very similar to the structures of other known HiPIPs, especially in the region proximal to the [Fe₄S₄] cluster, while the largest differences are observed on the opposite side of the protein, which is rich in positive charges and has no sequential homology to other HiPIP families.