Protein-polymer conjugates fuse together the synthetic and biologic worlds and are created in hopes of extending a protein’s natural function. Moving past traditional PEGylation techniques, where a chain of polyethylene glycol (PEG) is reacted with a protein, unique polymers with a range of varying attributes can now be grown-from the surfaces of proteins with controlled densities. This means that many protein-polymer conjugate variants can be synthesized and used to study how the various polymers impact protein function to develop structure-function-dynamic based relationships. Currently, it is impossible to predict the ultimate fate that the covalent attachment of polymers will have on a protein’s activity and long-term stability and this is partially due to a lack of insight into what interactions are occurring at the interface between the protein-polymer. Elucidating these interactions could help explain how different polymer types and molecular weights either increase or decrease activity in both native and non-native environments, including low pH. The scales of these interactions are on the Ångström level and can be difficult to probe experimentally in the laboratory. Computational models of protein-polymer conjugates, however, can be built <i>in silico</i> and molecular dynamics simulations can be performed in order to visualize dynamic motions and interactions with atomic resolution.<br/>Herein, we sought to determine how covalently attached polymers impact the activity and stability of our model protein, α-chymotrypsin, as a function of polymer type and molecular weight (polymer charge and length). We synthesized 15 related protein-polymer conjugate variants and measured changes in Michaelis-Menten activities and pH 1 acid stabilities. We further used molecular dynamics simulations to deepen our understanding of how polymers impact conjugate activities. Finally we propose a new mechanism for how polymers stabilize proteins in acid by modulating protein folding.

Structure-function-dynamics relationships in next generation protein-polymer conjugates

2019 Spring National Meeting

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