Abductin
Abductin is a naturally occurring elastomeric protein found in the hinge ligament of bivalve mollusks.
It is unique as it is the only natural elastomer with compressible elasticity, as compared to resilin, spider silk, and elastin.
In spite of these differences, the same general function of acting opposite of the abductor muscles, where the resilin forces the shells into an open configuration.
Further analysis showed that abductin is made of three prominent amino acids: glycine, methionine, and phenylalanine, which are arranged in multiple repeating sequences throughout the molecule.
[4] The high concentration of methionine found in abductin makes it unique because it is not a common occurrence in natural elastomeric proteins.
[7] The effectiveness of abductin is highly influenced by the morphological aspects of the mollusk's shell, such as its size and shape.
An understanding of the underlying structural features of these proteins may lead to the development of a new class of highly tailored ‘‘compressible’’ hydrogels.
[9] The secondary structure of abductin was also investigated by Nuclear Magnetic Resonance (NMR) and CD studies of several synthetic peptides.
The coexistence of PPII and type II β-turns and temperature-induced multiconformational transitions were observed with longer synthetic abductin-like peptides such as (FGGMGGGNAG)4 in hexafluoroisopropanol (HFIP).
In addition, because the peak at 218 nm never exceeds zero, the spectra suggest the coexistence of unordered structures and PPII helices.
With increasing temperature, the magnitude of both peaks in the CD spectra at 200 and 218 nm decreased, which is typical for PPII helix conformations.
[11] The abductin-based protein possessed reversible Upper Critical Solution Temperature (UCST) behavior and formed a gel-like structure.
[11] A LIVE/DEAD assay revealed that human umbilical vein endothelial cells had a viability of 98 ± 4% after being cultured for two days on the abductin-based protein.
These studies thus demonstrate the potential of abductin-based proteins in tissue engineering and drug delivery applications due to the cytocompatibility and its response to temperature.
The superior mechanical properties of natural abductin offer the potential for designing protein-based biomaterials that can be utilized in a broader number of applications.
[13] As of April 2022, there hasn’t been large-scale production, nor application, of polymers derived from the abductin or related polymeric sequences.
