title: Subunit interaction slows the unfolding of the N-terminal domain of creatine kinase in urea.
abstract: Fluorescence emission intensity changes with two different excitation wavelengths were used to measure the unfolding rate constants of different domains of muscle type creatine kinase (CK-MM) according to the heterogeneity of aromatic amino acid distributions in the crystal structure of CK-MM. The results were compared with those of brain type creatine kinase (CK-BB) and dithio-bis(succinimidyl propionate) cross-linked CK-MM. CK-BB differed greatly in its distribution of aromatic amino acids in each domain and the unfolding process of cross-linked CK-MM was not accompanied by the dissociation of the dimer. The N-terminal domain of CK-MM was shown to be well protected by subunit interaction during the unfolding of CK-MM in 4 M urea. Dissociating the CK dimer in high urea concentration (> or = 6 M) eliminated the subunit protection. Subunit interactions are also important in preserving secondary structure and forming contracted conformation at low urea concentration.
authors.affiliation: Department of Biological Science and Biotechnology, School of Life Science and Engineering, Tsinghua University, Beijing 100084, China.
authors.forename: Z
authors.initials: Z
authors.lastname: Guo
authors.forename: Z
authors.initials: Z
authors.lastname: Wang
authors.forename: X C
authors.initials: XC
authors.lastname: Wang
mesh_terms: D002942:Circular Dichroism; D003402:Creatine Kinase / Q000737:chemistry*; D003432:Cross-Linking Reagents / Q000494:pharmacology; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D011489:Protein Denaturation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D013696:Temperature; D013997:Time Factors; D014508:Urea / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D014508:Urea; D003402:Creatine Kinase