2026-04-07 東京大学
アコヤガイ貝殻とLICPのアラゴナイトナノファイバー形成模式図
＜関連情報＞
- https://www.a.u-tokyo.ac.jp/topics/topics_20260407-1.html
- https://www.pnas.org/doi/10.1073/pnas.2522686123
アコヤガイの蝶番靭帯に含まれるLICPのアラゴナイトナノファイバー形成機構の解明 Elucidation of the aragonite nanofiber formation mechanism of LICP contained in the hinge ligament of Pinctada fucata
Kei Futagawa, Yuto Namikawa, Taichi Morioka +12 , and Michio Suzuki
Proceedings of the National Academy of Sciences Published:April 7, 2026
DOI:https://doi.org/10.1073/pnas.2522686123
Significance
Understanding how proteins control crystal growth on solid surfaces is essential in biomineralization, materials science and protein sciences. Ligament intracrystalline peptide (LICP) controls the crystal orientation and growth in the aragonite nanofiber. The structural relationship between LICP and the aragonite surface provides key insights into nonclassical organic–inorganic interactions, as it reveals detailed structural dynamics of the peptide, including side-chain orientations, on the mineral surface. In this study, we used the synthetic peptide with the full-length including a posttranslational modification. The specific binding of LICP to {hk0}—all planes parallel to the c-axis—and elongation of the c-axis provide design principles for peptide-based control of aragonite nanofibers and other inorganic crystal in materials science and protein sciences.
Abstract
The hinge ligament of bivalves exhibits remarkable flexibility and compressive strength due to its composite structure of aragonite nanofibers embedded in an organic matrix. While these nanofibers are crucial for shell mechanics, the molecular mechanisms underlying their formation remain unclear. We investigated the function of a 10-residue intracrystalline peptide, ligament intracrystalline peptide (LICP), in regulating aragonite crystal growth. Using a solution-state NMR technique optimized for biomineral systems with dispersive calcium carbonate particles, we showed that LICP adopted a planar, elongated conformation in binding to aragonite. This structure features a coplanar arrangement of carboxyl and aromatic side chains—particularly tyrosines—that enables selective interaction with the aragonite {110}. Saturation transfer difference NMR and dose-dependent structural analyses confirmed that this conformational change is triggered by solid-phase contact, rather than free calcium ions. Molecular dynamics simulations revealed enhanced binding stability of LICP to the {110} surface through multiple carboxyl and aromatic residues. Furthermore, in vitro crystallization assays showed that LICP promoted elongation of aragonite crystals along the c-axis, consistent with its selective surface binding. These findings demonstrated that conformational plasticity in short, disordered peptides enabled specific recognition of crystal faces and directed modulation of mineral growth. LICP serves as a minimal yet powerful model for exploring protein–mineral interfaces, offering broader insights into the structural principles by which intrinsically disordered peptides function in solid-phase biological systems.
