The properties of proteins can be improved by covalent conjugation with polymers. Rational design of these bioconjugates is obstructed by a lack of mechanistic understanding because of the absence of data on interactions between the protein and polymer. Does an attached polymer behave like a random coil or interact with the protein such that it wraps around the surface? Here, we have employed paramagnetic relaxation enhancement (PRE) as a tool for identifying interactions between the polymer and the surface of the protein. We observed interactions between a spin-labeled polymer and the surface of the conjugate protein, even when spin labels are 25 monomer units away from the conjugation site, indicating that polymer wrapping is occurring in this system. Significant stabilization against chemical denaturation by guanidine was observed by circular dichroism (CD) in these bioconjugates as compared to the wild type protein. We attribute this stabilization to interactions between the protein and polymer as the PRE data points to the polymer localizing around the nonpolar β-sheet face of Ub.
Author: Caleb Kozuszek
Faculty Advisor: Dominik Konkolewicz
Graduate Student Advisor: Kevin Burridge
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