title: Stabilization of amorphous calcium carbonate by phosphate rich organic matrix proteins and by single phosphoamino acids.
abstract: Stable amorphous calcium carbonate (ACC) is a unique material produced naturally exclusively as a biomineral. It was demonstrated that proteins extracted from biogenic stable ACC induce and stabilize synthetic ACC in vitro. Polyphosphate molecules were similarly shown to induce amorphous calcium carbonate formation in vitro. Accordingly, we tested the hypothesis that biogenic ACC induction and stabilization is mediated by the phosphorylated residues of phosphoproteins. We show that extracellular organic matrix extracted from gastroliths of the red claw crayfish Cherax quadricarinatus induce stable ACC formation in vitro. The proteinaceous fraction of this organic matrix is highly phosphorylated and is incorporated into the ACC mineral phase during precipitation. We have identified the major phosphoproteins of the organic matrix and showed that they have high calcium binding capacity. Based on the above, in vitro precipitation experiments with single phosphoamino acids were performed, indicating that phosphoserine or phosphothreonine alone can induce the formation of highly stable ACC. The results indicate that phosphoproteins may play a major role in the control of ACC formation and stabilization and that their phosphoamino acid moieties are key components in this process.
authors.affiliation: Department of Biotechnology Engineering, Ben-Gurion University of the Negev, 84105, Israel.
authors.forename: Shmuel
authors.initials: S
authors.lastname: Bentov
authors.forename: Simy
authors.initials: S
authors.lastname: Weil
authors.forename: Lilah
authors.initials: L
authors.lastname: Glazer
authors.forename: Amir
authors.initials: A
authors.lastname: Sagi
authors.forename: Amir
authors.initials: A
authors.lastname: Berman
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000737:chemistry / Q000378:metabolism; D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism*; D008297:Male; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D019606:Phosphoamino Acids / Q000737:chemistry / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D013059:Spectrum Analysis, Raman
chemical_list: D019606:Phosphoamino Acids; D010750:Phosphoproteins; D002119:Calcium Carbonate