Structure of human muscle creatine kinase

The crystal structure of human muscle creatine kinase has been determined b y the molecular-replacement method and refined at 3.5 Angstrom resolution. The structures of both the monomer and the dimer closely resemble those of the other known structures in the creatine kinase family. Two types of dime rs, one with a non-crystallographic twofold symmetry axis and the other wit h a crystallographic twofold symmetry axis, were found to occur simultaneou sly in the crystal. These dimers form an infinite 'double-helix'-like struc ture along an unusual long crystallographic 3(1) axis.