Structure, Self-Assembly, and Dual Role of a β-Defensin-like Peptide from the Chinese Soft-Shelled Turtle Eggshell Matrix

Biomineral matrix formation and molecular recognition are two important processes associated with eggshell biomineralization. To understand these two processes, a major intracrystalline peptide, pelovaterin, was isolated from turtle (Pelodiscus sinensis) eggshell and its tertiary and quaternary structures were established. The global fold of pelovaterin is similar to that of human β-defensins but has a large hydrophobic core and a short hydrophilic N-terminal segment, which is not preserved in defensins. Pelovaterin exhibits strong antimicrobial activity against two pathogenic Gram-negative bacteria, Pseudomonas aeruginosa and Proteus vulgaris, and stabilizes a thin film of metastable vaterite. We show that pelovaterin self-aggregates in the form of micellar nanospheres and the aggregation in solution is entropy-driven. It is suggested that the micellar aggregation of pelovaterin is responsible for the induction and stabilization of the metastable phase by altering the interfacial energy. The results demo...