Interfacial Mineral–Peptide Properties of a Mineral Binding Peptide from Osteonectin and Bone-like Apatite

Abstract

Osteonectin is a regulator of bone mineralization. It interacts specifically with collagen and apatite through its N-terminal domain, inhibiting crystal growth. In this work, we investigated the interface formed between the mineral and an acidic peptide, ON29, derived from the protein's apatite binding domain. The structural properties of the peptide bound to the mineral and the mineral−peptide interface are characterized using NMR and computational methods. A biomaterial complex is formed by precipitation of the mineral in the presence of the acidic peptide. The peptide gets embedded between mineral particles, which comprise a disordered hydrated coat covering apatite-like crystals. 31 P SEDRA measurements show that the peptide does not affect the overall proximity between phosphate ions in the mineral. { 15 N} 13 C REDOR measurements reveal an α-turn in the center of the free peptide, which is unchanged when it is bound to the mineral. { 31 P} 13 C REDOR and 1 H− 13 C HETCOR measurements show that Glu/Asp carboxylates and Thr/Ala/Val side chains from ON29 are proximate to phosphate and hydroxyl groups in the mineral phases. Predictions of ON29's fold on and off hydroxyapatite crystal faces using ROSETTA-surface are used to model the molecular conformation of the peptide and its apatite-binding interface. The models constructed without bias from experimental results are consistent with NMR measurements and map out extensively the residues forming an interface with apatitic crystals.

Engineering l-asparaginase for spontaneous formation of calcium phosphate bioinspired microreactors

“…The homonuclear decoupling employed in t 1 effectively removes water proton excitation, and therefore no correlations are observed between water and phosphate species. This is quite different from other preparations of apatite minerals, 53,57 whereby a strong correlation of water protons with phosphates in a disordered calcium phosphate layer on HA crystallites was observed. The absence of the water resonance in the 2D HETCOR spectra is further demonstrated in the 1 H projections (taken along the phosphate maximal intensity) of 53 ).…”

Apatite minerals derived from collagen phosphorylation modification induce the hierarchical intrafibrillar mineralization of collagen fibers

“…Apatite minerals nucleate, crystallize and grow along the arrangement direction of ColI fibrils, then form the extrafibrillar and intrafibrillar biomineralized ColI in vitro with the regulation of noncollagenous proteins (NCPs) (C. Liu et al, ; Moon et al, ; Ping et al, ; Zhang & Wang, ). Some polyphosphate compounds can replace NCPs to regulate ColI biomimetic mineralization as template analogues (Dey et al, ; Y. Y. Hu et al, ; Matlahov et al, ; X. F. Niu, Feng, Wang, Guo, & Zheng, ; Nudelman, Lausch, Sommerdijk, & Sone, ). Polyvinylphosphonic acid, sodium trimetaphosphate (STMP), and sodium tripolyphosphate (STPP) are the frequently‐used chemical phosphorylation agents for proteins and they were also used in biomimetic mineralization of ColI fibers (Gu et al, ; Gu et al, ; X. Li & Chang, ; Y. Liu, Li, Qi, Niu, et al, ).…”

Osteopontin regulates biomimetic calcium phosphate crystallization from disordered mineral layers covering apatite crystallites

“…Previous TGA measurements of HAP•ON29 showed that the peptide constitutes 4.8 weight% (1.6 mol%) of the material. Similarly, TGA of HAP•umOC showed that umOC constitutes 8.0 weight% of the material (1.4 mol%) 26,28 . Molar content of qOPN in the protein-mineral composite formed is much lower than ON29 or umOC.…”

“…The dense crystallite aggregates observed in the scanning electron micrographs of HAP•qOPN relative to HAP resemble the ones recorded on HAP•ON29. They may be caused by strong adsorption forces of the biomolecules which can adhere to more than one crystallite thereby inducing aggregation by agglutination 27,28 . This also manifested in the lower SSA measured for HAP•qOPN than for HAP or for HAP•ON29.…”

“…The existence of such intermediate mineral phase alleviates the stringent transition from a completely disordered hydrated phase to a highly ordered core crystalline phase. ON29 and umOC co-precipitated with the mineral were capable of changing the content of HPO 4 2− ions and water molecules in the hydrated layer as well [26][27][28][29] . These findings open new questions regarding the capabilities possessed by non-collagenous proteins, for regulating and modifying the mineral phases via organic-inorganic interactions.…”