Effect of Single-Point Sequence Alterations on the Aggregation Propensity of a Model Protein - Analytical Methods & Tools for Lyophilization

Effect of Single-Point Sequence Alterations on the Aggregation Propensity of a Model Protein
Received October 6, 2005
Web Release Date: January 12, 2006
Dusan Bratko,* Troy Cellmer, John M. Prausnitz, and Harvey W. Blanch
J. Am. Chem. Soc.
ACS Publications
Copyright © 2006 American Chemical Society
Contribution from the Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, Department of Chemical Engineering, University of California, Berkeley, California 94720, and Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
dbratko@vcu.edu
Abstract:
Sequences of contemporary proteins are believed to have evolved through a process that optimized their overall fitness, including their resistance to deleterious aggregation. Biotechnological processing may expose therapeutic proteins to conditions that are much more conducive to aggregation than those encountered in a cellular environment. An important task of protein engineering is to identify alternative sequences that would protect proteins when processed at high concentrations without altering their native structure associated with specific biological function. Our computational studies exploit parallel tempering simulations of coarse-grained model proteins to demonstrate that isolated amino acid residue substitutions can result in significant changes in the aggregation resistance of the protein in a crowded environment while retaining protein structure in isolation. A thermodynamic analysis of protein clusters subject to competing processes of folding and association shows that moderate mutations can produce effects similar to those caused by changes in system conditions, including temperature, concentration, and solvent composition, that affect the aggregation propensity. The range of conditions where a protein can resist aggregation can therefore be tuned by sequence alterations, although the protein generally may retain its generic ability for aggregation.
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