title: Bio-vaterite formation by glycoproteins from freshwater pearls.
abstract: A 48 kDa acidic and putative calcium-binding glycoprotein was isolated from pearls of the freshwater mussel Hyriopsis cumingii. This protein was compared with a related 46 kDa polypeptide, obtained from the nacreous shell of the same species. Separation by two-dimensional gel electrophoresis revealed that the difference in molecular weight is due to the higher extent of glycosylation of the 48 kDa protein existing in pearls. Evidence is presented that the sugar moieties of the protein contribute to crystal growth, starting with the nucleation step. In in vitro precipitation experiments, the 48 kDa glycoprotein of pearls directed the formation of round-shaped vaterite crystals while the 46 kDa glycoprotein of shells promoted formation of small irregular calcite particles. Furthermore, both proteins, 48 kDa/46 kDa, comprised carbonic anhydrase activity that has been implicated in CaCO(3) formation. Thus, a function of the isolated glycoproteins in biomineralization is proposed together with the mechanism by which they can stabilize different calcium carbonate polymorphs.
authors.affiliation: Institute for Physiological Chemistry and Pathobiochemistry, Johannes Gutenberg University, Medical School, Duesbergweg 6, D-55099 Mainz, Germany.
authors.forename: Antonino
authors.initials: A
authors.lastname: Natoli
authors.forename: Matthias
authors.initials: M
authors.lastname: Wiens
authors.forename: Heinz-Christoph
authors.initials: HC
authors.lastname: Schröder
authors.forename: Mauro
authors.initials: M
authors.lastname: Stifanic
authors.forename: Renato
authors.initials: R
authors.lastname: Batel
authors.forename: Analia L
authors.initials: AL
authors.lastname: Soldati
authors.forename: Dorrit E
authors.initials: DE
authors.lastname: Jacob
authors.forename: Werner E G
authors.initials: WE
authors.lastname: Müller
mesh_terms: D000818:Animals; D002119:Calcium Carbonate / Q000378:metabolism*; D002256:Carbonic Anhydrases / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D005618:Fresh Water; D006023:Glycoproteins / Q000737:chemistry / Q000302:isolation & purification* / Q000378:metabolism*; D006031:Glycosylation; D008970:Molecular Weight; D049876:Unionidae / Q000737:chemistry*
chemical_list: D006023:Glycoproteins; D002256:Carbonic Anhydrases; D002119:Calcium Carbonate