Abstact

Highly-ordered protein structures have gained interest for future uses for biomaterials. Herein, we constructed a building block protein (BBP) by the circular permutation of the hyperthermostable Aquifex aeolicus cytochrome (cyt) c(555) , and assembled BBP into a triangle-shaped trimer and a tetrahedron. The angle of the intermolecular interactions of BBP was controlled by cleaving the domain-swapping hinge loop of cyt c(555) and connecting the original N- and C-terminal alpha-helices with an alpha-helical linker. We obtained BBP oligomers up to approximately 40 mers, with a relatively large amount of trimers. According to the X-ray crystallographic analysis of the BBP trimer, the N-terminal region of one BBP molecule interacted intermolecularly with the C-terminal region of another BBP molecule, resulting in a triangle-shaped structure with an edge length of 68 A. Additionally, four trimers assembled into a unique tetrahedron in the crystal. These results demonstrate that the circular permutation connecting the original N- and C-terminal alpha-helices with an alpha-helical linker may be useful for constructing organized protein structures.