Cutinase Immobilization on a Supramolecular Cage Protein Scaffold

Self-assembly of preformed nanoparticles into larger and more complex materials, termed nanoarchitectonics, is an area of great interest as the resulting higher-order architectures can exhibit advanced supramolecular properties important in sensor design, catalysis, and ferromagnetic properties. The aim of the current investigation is to explore the application of self-assembling protein networks to serve as molecular scaffolds for immobilization of enzyme catalysts. The use of 12 nm ferritin cage proteins to serve as components of these scaffolds would expand the application of these types of multifunctional proteins to the fabrication of advanced biomaterials. Humicola insolens cutinase was immobilized on a supramolecular protein scaffold using bioconjugation to biotinylate the enzyme of interest. The protein-based scaffold consisted of a ferritin- biotin-avidin system, and the interaction of biotin and avidin was used to suspend the enzyme molecules onto this network. Matrix-assisted laser desorption mass spectrometry, scanning electron microscopy, and energy dispersive X-ray spectroscopy were employed to analyze the supramolecular cage protein scaffold at various stages of fabrication. The activities of these scaffold-bound enzymes towards chromogenic esters and polyethylene terephthalate (PET) were analyzed and found to remain active towards both substrates following biotinylation and immobilization. Biotinylated Humicola insolens cutinase enzymes can be immobilized on nanodimensional protein networks composed of avidin and biotinylated horse spleen ferritin and exhibit catalytic activity toward a small substrate, p-nitrophenylbutyrate, as well as an industrial plastic. Selfassembling protein networks may provide new approaches for biomolecular immobilization.