Pancreatic Lithostathine as a Calcite Habit Modifier

Abstract

Most biological fluids are supersaturated with calcium salts. A mechanism controlling crystal growth is therefore necessary to prevent excessive precipitation and development of a lithiasis. In pancreatic juice, calcite precipitation is prevented by lithostathine, a glycoprotein that inhibits calcite crystal growth. We describe here the interaction of lithostathine with calcite crystals. Without lithostathine, calcite crystals grew as rhombohedra showing six (104) faces. At low concentration (1 microM), lithostathine already altered crystal growth by generating new (110) faces. At physiological concentrations (3-10 microM), adsorption resulted in a transition from rhombohedral to sub-cubic habits. Immunochemical localization demonstrated that, although all (104) faces are equivalent, lithostathine binding was restricted to the face edges distal to the c axis. Scanning electron microscopy showed that, at the site of lithostathine binding, spreading of new CaCO3 layers during crystal growth was arrested before reaching the crystal diad axis-bearing edges. The successive kinks generated during crystal growth formed the new, striated (110)faces. Similar modifications were observed with the N-terminal undecapeptide of lithostathine that bears the inhibitory activity. With 100 microM lithostathine, (110) faces could reach the c axis outcrop of the former rhombohedron, resulting in an olive-shaped crystal. Finally, the number of crystals increased and their average size decreased when lithostathine concentration increased from 0.1 to 100 microM. Decreased Ca2+ concentration during crystal growth was delayed in the presence of lithostathine. It was concluded that lithostathine controls lithogenesis 1) by triggering germination of numerous calcite crystals and 2) by inhibiting the rate of Ca2+ ion apposition on the nuclei and therefore interfering with the apposition of new layers on calcite. Formation of smaller crystals, whose elimination is easier, is thereby favored.

Intrinsically Disordered Proteins in Biomineralization

“…Structural studies of ovocleidin-17 and ansocalcin revealed that their three-dimensional structure is very similar to the structure of lithostathine (Bertrand et al, 1996;Lakshminarayanan et al, 2005;Reyes-Grajeda et al, 2004); however, the three proteins had different effects on calcium carbonate crystals. Lithostathine was an inhibitor, ansocalcin caused the formation of crystal aggregates, and ovocleidin-17 led to the crystals twinning (but not to an extensive aggregation of crystals like with ansocalcin) (Geider et al, 1996;Lakshminarayanan et al, 2005). It should be noted that N-terminal regions of ansocalcin and ovocleidin-17 are well folded, while lithostathine's N-terminus is disordered.…”

DC-SIGN Binds to HIV-1 Glycoprotein 120 in a Distinct but Overlapping Fashion Compared with ICAM-2 and ICAM-3

“…DC-SIGN contains the highly conserved Glu-Pro-Asn (EPN) motif and thus belongs to the mannose-specific family of lectins (31). Nonetheless, the CRDs of C-type lectins can recognize a remarkably broad range of ligands and have also been shown to bind specifically to proteins (34), lipids (35), and inorganic molecules such as calcium carbonate (36). Moreover, some CRDs are able to bind to both protein and saccharide ligands (37,38).…”

Acceleration of Calcite Kinetics by Abalone Nacre Proteins

“…In contrast, studies using full proteins were non-quantitative and underlying sources of growth modification were ill-defined. [7,8] Here we investigate interactions between proteins isolated from abalone shell nacre and growing surfaces of calcite. We find that these proteins significantly accelerate the molecular-scale kinetics and, though much larger than atomic steps, alter growth morphology through stepspecific interactions that lower their free energies.…”