Crystal structure of brain-type creatine kinase at 1.41 angstrom resolution

Excitable cells and tissues like muscle or brain show a highly fluctuating consumption of ATP, which is efficiently regenerated from a large pool of p hosphocreatine by the enzyme creatine kinase (CK). The enzyme exists in tis sue-as well as compartment-specific isoforms. Numerous pathologies are rela ted to the CK system: CK is found to be overexpressed in a wide range of so lid tumors, whereas functional impairment of CK leads to a deterioration in energy metabolism. which is phenotypic for many neurodegenerative and age- related diseases. The crystal structure of chicken cytosolic brain-type cre atine kinase (BB-CK) has been served to 1.41 Angstrom resolution by molecul ar replacement. It represents the most accurately determined structure in t he family of guanidino kinases. Except for the N-terminal region (2-12), th e structures of both monomers in the biological dimer are very similar and closely resemble those of the other known structures in the family. Specifi c Ca2+-mediated interactions, found between two dimers in the asymmetric un it, result in structurally independent heterodimers differing in their N-te rminal conformation and secondary structure. The high-resolution structure of BB-CK presented in this work will assist in designing new experiments to reveal the molecular basis of the multiple isoform-specific properties of CK, especially regarding different subcellular locations and functional int eractions with other proteins. The rather similar fold shared by all known guanidino kinase structures suggests a model for the transition state compl ex of BB-CK analogous to the one of arginine kinase (AK). Accordingly, we h ave modeled a putative conformation of CK in the transition state that requ ires a rigid body movement of the entire N-terminal domain by rms 4 Angstro m from the structure without substrates.