title: The carp muscle-specific sub-isoenzymes of creatine kinase form distinct dimers at different temperatures.
abstract: We have previously cloned three muscle-specific sub-isoforms of creatine kinase (CK, EC 2.7.3.2) from the common carp ( Cyprinus carpio ), designated M1-CK, M2-CK, and M3-CK. The enzyme has a key role in maintaining the energy homoeostasis of cells with fluctuating energy requirements. In the present paper, we report that all three M-CKs in the red and white muscle of different temperature-acclimatized carp were ubiquitously distributed in the cytosol and along membranes. In addition, the expression levels of these isoforms were not significantly altered in response to the temperature acclimatization. Interestingly, our studies showed that the formation of distinct homo- or heterodimers among these three M-CKs was found at various temperatures. At higher temperature, the M1M1-CK and M2M2-CK homodimers, and the M1M3-CK heterodimer are the predominant MM-CKs, whereas the M3M3-CK achieves its homodimeric state at lower temperature. We postulated testable homology models to investigate the chemical properties of these dimeric interfaces. M1M1-CK was used as a reference to compare the structural differences with the M3M3-CK dimer. The calculated solvent accessible surface area that was buried in the contact interfaces of the M1M1-CK and M3M3-CK dimers showed an overall decrease of 12% in the M3M3-CK interface. The modelling analysis also suggested a net decrease of twelve hydrophobic residues and a Phe(3)-->Lys substitution in the M3M3-CK interface. An increase in thermolability of the M3M3-CK homodimer might be due to the decrease in subunit ion pairs and buried surface area in this dimer. Based on our findings, we propose that the carp-muscle-specific CK isoenzymes could undergo shuffling to form distinct M-CK homo- or heterodimers in acclimatization to environmental temperatures.
authors.affiliation: Graduate Institute of Life Science, National Defense Medical Center, Taipei 117, Taiwan.
authors.forename: Hsi-Wen
authors.initials: HW
authors.lastname: Sun
authors.forename: Cheng-Wen
authors.initials: CW
authors.lastname: Liu
authors.forename: Cho-Fat
authors.initials: CF
authors.lastname: Hui
authors.forename: Jen-Leih
authors.initials: JL
authors.lastname: Wu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002347:Carps; D002462:Cell Membrane / Q000201:enzymology; D003402:Creatine Kinase / Q000737:chemistry* / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005982:Glutathione Transferase / Q000378:metabolism; D015151:Immunoblotting; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009132:Muscles / Q000201:enzymology*; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017386:Sequence Homology, Amino Acid; D013696:Temperature
chemical_list: D020033:Protein Isoforms; D005982:Glutathione Transferase; D003402:Creatine Kinase