Influence of Cell-free Proteins in the Nucleation of CaCO3 Crystals in Calcified Endoskeleton

Authors: M. Azizur Rahman, Tamotsu Oomori

Abstract:

Calcite aCalcite and aragonite are the two common polymorphs of CaCO3 observed as biominerals. It is universal that the sea water contents a high Mg2+ (50mM) relative to Ca2+ (10mM). In vivo crystallization, Mg2+ inhibits calcite formation. For this reason, stony corals skeleton may be formed only aragonite crystals in the biocalcification. It is special in case of soft corals of which formed only calcite crystal; however, this interesting phenomenon, still uncharacterized in the marine environment, has been explored in this study using newly purified cell-free proteins isolated from the endoskeletal sclerites of soft coral. By recording the decline of pH in vitro, the control of CaCO3 nucleation and crystal growth by the cellfree proteins was revealed. Using Atomic Force Microscope, here we find that these endoskeletal cell-free proteins significantly design the morphological shape in the molecular-scale kinetics of crystal formation and those proteins act as surfactants to promote ion attachment at calcite steps.nd aragonite are the two common polymorphs of CaCO3 observed as biominerals. It is universal that the sea water contents a high Mg2+ (50mM) relative to Ca2+ (10mM). In vivo crystallization, Mg2+ inhibits calcite formation. For this reason, stony corals skeleton may be formed only aragonite crystals in the biocalcification. It is special in case of soft corals of which formed only calcite crystal; however, this interesting phenomenon, still uncharacterized in the marine environment, has been explored in this study using newly purified cell-free proteins isolated from the endoskeletal sclerites of soft coral. By recording the decline of pH in vitro, the control of CaCO3 nucleation and crystal growth by the cell-free proteins was revealed. Using Atomic Force Microscope, here we find that these endoskeletal cell-free proteins significantly design the morphological shape in the molecular-scale kinetics of crystal formation and those proteins act as surfactants to promote ion attachment at calcite steps. KeywordsBiomineralization, Calcite, Cell-free protein, Soft coral

Keywords: Biomineralization, Calcite, Cell-free protein, Soft coral

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1084764

References:

[1] M. A. Rahman, T. Oomori, Structure, Crystallization and Mineral Composition of Sclerites in the Alcyonarian Coral, J. cryst. Growth, 310:3528-3534, 2008.
[2] L. Addadi, and S., Weiner, Interactions between Acidic Proteins and Crystals: Stereochemical Requirements in Biomineralization. Proc. Natl. Acad. Sci. USA 82, 4110-4114, 1985.
[3] S., Weiner, W. Traub, and H.A. Lowenstam, 1983. In: Biomineralization and Biological Metal Accumulation, eds Westbroek, P. & de Jong, EW (Reidel, Dordrecht, Holland), pp 205-224.
[4] M.J., Glimcher, 1981. In The Chemistry and Biology of Mineralized Connective Tissues, ed Veis. A (Elsevier, New York), pp 617-673.
[5] A. Veis, and B. Sabsay, 1983. In: Biomineralization and Biological Metal Accumulation, eds Westbroek, P & de Jong, EW (Reidel, Dordrecht, Holland), pp 273-284.
[6] S. Weiner, Organization of organic matrix components in mineralized tissues. Amer. Zool. 24, 945-951, 1984.
[7] M.A. Rahman, and Y. Isa, Characterization of proteins from the matrix of spicules from the alcyonarian, Lobophytum crassum. J. Exp. Mar. Biol. Ecol. 321, 71-82, 2005.
[8] M. A. Rahman, T. Oomori, In vitro regulation of CaCO3 crystal growth by the highly acidic proteins of calcitic sclerites in soft coral, Sinularia polydactyla, Conn. Tissue Res. (in press) DOI:10.1080/03008200802714933
[9] M.A. Rahman, Y. Isa, A. Takemura, T. Uehara, "Analysis of proteinaceous components of the organic matrix of endoskeletal sclerites from the alcyonarian, Lobophytum crassum, Calcif. Tissue Int., 78: 178- 185, 2006.
[10] M. A. Rahman, T. Oomori, Aspartic Acid-rich Proteins in Insoluble Organic Matrix Play a Key Role in the Growth of Calcitic Sclerites in Alcyonarian Coral, Chin J Biotech. 24: 2127−2128, 2008.
[11] M. A. Crenshaw, Biomineralization 1972, p. 6.
[12] S. Weiner, Aspartic acid-rich proteins: major components of the soluble organic matrix of mollusk shells, Calcif Tissue Int 29 (1979) 163-167.
[13] M. A. Crenshaw and H. Ristedt, in The Mechanisms of Mineralization in the Invertebrates and Plants, N. Watabe and K.M. Wilbur, Eds, (University of South Carolina Press, Columbia, 1976, p. 355.
[14] M.A. Rahman, Y. Isa, T. Uehara, "Studies on two Closely Related Species of Octocorallians: Biochemical and Molecular Characteristics of the Organic Matrices of Endoskeletal Sclerites," Mar. Biotechnol, 8: 415-424, 2006.
[15] M.A. Rahman, Y. Isa, T. Uehara, Proteins of calcified endoskeleton: II. Partial amino acid sequences of endoskeletal proteins and the characterization of proteinaceous organic matrix of spicules from the alcyonarian, Synularia polydactyla, Proteomics 5: 885-893, 2005.
[16] A.H. Borman, E.W. De Jong, M. Huizinga, P. Westbroek, In: Westbroek, P., de Jong, E.W. (eds.), Biomineralization and Biological Metal Accumulation, D Reidel publishing, Dordrecht, Boston, London 1983, p. 303.
[17] O.H. Lowry, N.J. Rosebrough, A.L. Farr, R.J. Randall) Protein measurement with the Folin phenol Reagent. J Biol Chem 193: 265-275, 1951.
[18] H. A. Lowenstam , S. Weiner, 1989. On Biomineralization (Chapter 5: Cnidaria), pp. 74-87.
[19] W.J. Schmidt, 1924. Die Bausteine des Tierkorpers in Polarisiertem Lichte. F. Cohen Verlag, Bonn.
[20] J.D. Termine, E.D. Eanes, K.M. Conn, Calcif. Tissue Int., 31: 247, 1980
[21] M.A. Rahman, T. Oomori, T. Uehara, Carbonic anhydrase in calcified endoskeleton: Novel activity in biocalcification in alcyonarian, Mar. Biotechnol. 10: 31-38, 2008.