Preparation of Amylose-Mimicking Polymers for the Purification of Maltose-Binding Protein

Abstract

Maltose-binding protein (MBP) is used as affinity tags for purifying recombinant proteins via amylose affinity gels. However, the gel often yields a low quantity of the purified protein due to the biodegradability and low water solubility of immobilized amylose. Herein, water-soluble, anti-biodegradation amylose-mimicking polymers are synthesized by polymerizing a maltose monomer with a norbornene group, then copolymerizing it with a glucose monomer and norbornene. The synthesized polymers are further modified via hydrogenation and hydroxylation to alter their properties. The binding affinities of these polymers, which are evaluated using a quartz crystal microbalance instrument, indicated their binding to MBP mimics that of amylose. Furthermore, the polymer is immobilized on an agarose gel to prepare an affinity gel for MBP, which absorbs concanavalin A and MBP before eluting them. However, only 15% of MBP is absorbed, with the majority passing through the gel. This indicates that maltose is short enough to efficiently absorb MBP. However, amylose-mimicking polymers have higher water solubilities and are easier to handle than amylose polymers, making them expected to exhibit a higher MBP absorbability. Hence, optimizing ligand length and structure is key to improving MBP binding. Further, designs should focus on enhancing stability and binding efficiency to improve affinity purification.