Subunit interaction slows the unfolding of the N-terminal domain of creatine kinase in urea |
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Authors: | Guo Z Wang Z Wang X C |
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Institution: | (1) Department of Biological Science and Biotechnology, School of Life Science and Engineering, Tsinghua University, Beijing, 100084, China |
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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 ( 6 M) eliminated the subunit protection. Subunit interactions are also important in preserving secondary structure and forming contracted conformation at low urea concentration. |
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Keywords: | creatine kinase N-terminal domain dithio-bis(succinimidyl propionate) cross-link subunit interaction |
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