A comparison of calcium binding inCallinectes sapidus premolt and postmolt cuticle homogenates: Implications for regulation of biomineralization

Abstract

Cuticle tissue homogenates (CTHs) from Callinectes sapidus premolt cuticle bound approximately 367% more Ca2+ ions than did those from the postmolt cuticle. The pH-stat assay which was used to compare in vitro CaCO3 nucleation times confirmed that the premolt CTHs had greater inhibitory activity than did the postmolt CTHs. This inhibitory activity was indicated by CaCO3 nucleation times in excess of control values. Premolt nucleation times exceeded those of postmolt samples by approximately 340%. A positive correlation was observed between Ca2+ binding and calcification inhibitory activity for both premolt and postmolt CTHs. Heat pretreatment of CTHs at 70 degrees C for a 24-hr period had no significant effect on their Ca2+ binding. However, this heat pretreatment decreased their calcification inhibitory activity. Pretreatment of CTHs with Ca2+ diminished their calcification inhibitory activity. These results are consistent with a mechanism for inhibition of biocalcification by these proteins which involves their initial reversible binding to nascent calcite nuclei growth steps and kinks, rather than their in vivo interaction with free Ca2+ ions in solution.

Biological Calcification

“…Glycosaminoglycans have been described in initial calcification sites (the interprismatic septa) of the crab exocuticle, which also proved to contain carbonic anhydrase (Giraud-Guille 1984). Proteins have been detected by polyacrylamide gel electrophoresis of water soluble extracts from the uncalcified premolt cuticle of the blue crab Collinectes sapidus, but not from the calcified postmolt cuticle, so that the role of being calcification inhibitors has been attributed to them (Burgess et al 1992;Burgess and Oxendine 1995). Postecdysial cuticle alteration in the blue crab, Callinectes sapidus, involves the disappearance of 66 and 79 kDa glycoproteins at the onset of calcification (Shafer et al 1995).…”

Biomimetic Synthesis of Macroscopic-Scale Calcium Carbonate Thin Films. Evidence for a Multistep Assembly Process

“…Various acidic proteins extracted from biological minerals have shown the remarkable ability to inhibit crystal growth or to modify crystal habit. , In different extracts, both specific and nonspecific protein−mineral interface interactions have been identified. On the basis of specific interactions, small molecules or small peptides have been “tailor-made” to affect crystal morphology by inhibiting the growth of particular crystal faces.…”