The three-dimensional structure of cytosolic bovine retinal creatine kinase

Creatine kinase (CK) catalyses the reversible transfer of the phosphate moi ety from phosphocreatine (PCr) to ADP, generating creatine and ATP. The cry stal structure of a cytosolic brain-type creatine kinase is reported at 2.3 Angstrom. The biological dimer sits on a crystallographic twofold axis. Th e N-terminal residues of both subunits come very close to the crystallograp hic twofold at the dimer interface. The electron density observed is consis tent with two alternative conformations for the N-termini, as previously fo und for chicken brain-type creatine kinase.