Scallop Abductin Translates Hydrophobicity to Elasticity

Felipe Jimenez , Mario Blanco , William A. Goddard , and Lawrence B. Sandberg

Jerry L. Pettis Memorial Veterans Medical Center and Loma Linda University

California Institute of Technology

Abstract

Peptide mapping of Abductin, a major component of the abductor ligament in the swimming scallop Placopecten magellanicus, revealed a repeating pentapeptide sequence, FGGMG. The same sequence was previously found to occur eight times in the 119 amino acid Abductin sequence for the scallop, Argopecten irradians. The tertiary structure of the repeat sequence from the Argopecten Abductin containing FGGMG, as obtained from extensive molecular dynamics calculations in the presence of a solvent, reveals the presence of partially exposed hydrophobic pockets. A combination of covalent cross-links and these hydrophobic domains may explain the compressional stability and biphasic nature of Abductin. Using molecular dynamics and solid phase peptide synthesis, we designed and synthesized a peptide mimetic of Abductin that self-assembles into a biphasic aggregate with rubber-like properties even in the absence of covalent cross-links. The elastic behavior of this novel biomaterial, manifested by the formation of a rubber-like solid, suggests that hydrophobic microdomains lead to "hydrophobic cross-linking", an extreme form of molecular self-assembly as yet unreported in the literature. Further analysis seem to suggest that hydrophobic microdomains not only play a role in molecular self-assembly but also in conferring a free energy driving force for compressional elasticity. We hereby propose a hydroelasticity model that elucidates the relative contribution of hydrophobic moieties in producing elastic recoil in natural bioelastomers.