Conformational analysis of biomineral proteins with intrinsically disordered regions interacting with solid calcium carbonate using dispersive calcium carbonate particles for solution NMR

Biomineral proteins play critical roles in controlling the polymorph, orientation, and morphology of calcium carbonate (CaCO3) in mollusk shells. Many of these proteins are intrinsically disordered and contain low-complexity regions (IDPs). Structural and functional analyses of IDPs are highly challenging because of their structural flexibility. This mini review highlights recent research elucidating the conformational changes and mineral-binding mechanisms of two representative biomineral proteins from Pinctada fucata: Pif 80, which promotes tablet-shaped aragonite formation in the nacreous layer, and ligament methionine-rich protein, which facilitates the organization of aragonite nanofibers in the hinge ligament. Using solution nuclear magnetic resonance in combination with CaCO3 dispersive particles, we characterized structural transitions in short repeat peptides derived from these proteins. These findings provide insight into the molecular mechanisms underlying organic-inorganic interactions during biomineralization and offer principles for designing bioinspired materials with controllable mineralization properties.