Module 3: Figure CSQ polymerization
A model of calsequestrin polymerization to form Ca2+-decorated fibrils.
A. In the absence of Ca2+, the unfolded monomer is in an extended state because of the charge repulsion of its many negatively charged amino acids. B and C. As Ca2+ begins to bind, the charge repulsion is shielded, and the protein begins to fold up into its characteristic tertiary structure. D. The monomers then form front-to-front dimers. E. The dimers then form front-to-back tetramers. F. The tetramers then polymerize further to form the long fibrils. Reproduced from Figure 6 in Park, H., Wu, S., Dunker, A.K. and Kang, C. (2003) Polymerization of calsequestrin. Implications for Ca2+ regulation. J. Biol. Chem. 278:16176–16182, with permission from the American Society for Biochemistry and Molecular Biology; see Park et al. 2003.