Oligomerization enhancement and two domain swapping mode detection for thermostable cytochrome c552 via the elongation of the major hinge loop.

High-order oligomers of Hydrogenobacter thermophilus cytochrome c552 increased with the insertion of more Gly residues between Ala18 and Lys19 at the major hinge loop of the wild-type protein. N-Terminal domain swapping and C-terminal domain swapping were elucidated by using X-ray crystallography for the mutant with the insertion of three Gly residues at the hinge loop.