Mutation choice to eliminate buried free cysteines in protein therapeutics.Xia, X., Longo, L.M., Blaber, M.
(2015) J Pharm Sci 104: 566-576
- PubMed: 25312595
- DOI: https://doi.org/10.1002/jps.24188
- Primary Citation of Related Structures:
4Q91, 4Q9G, 4Q9P, 4QAL, 4QBC, 4QBV, 4QC4
- PubMed Abstract:
Buried free-cysteine (Cys) residues can contribute to an irreversible unfolding pathway that promotes protein aggregation, increases immunogenic potential, and significantly reduces protein functional half-life. Consequently, mutation of buried free-Cys residues can result in significant improvement in the storage, reconstitution, and pharmacokinetic properties of protein-based therapeutics. Mutational design to eliminate buried free-Cys residues typically follows one of two common heuristics: either substitution by Ser (polar and isosteric), or substitution by Ala or Val (hydrophobic); however, a detailed structural and thermodynamic understanding of Cys mutations is lacking. We report a comprehensive structure and stability study of Ala, Ser, Thr, and Val mutations at each of the three buried free-Cys positions (Cys16, Cys83, and Cys117) in fibroblast growth factor-1. Mutation was almost universally destabilizing, indicating a general optimization for the wild-type Cys, including van der Waals and H-bond interactions. Structural response to Cys mutation characteristically involved changes to maintain, or effectively substitute, local H-bond interactions-by either structural collapse to accommodate the smaller oxygen radius of Ser/Thr, or conversely, expansion to enable inclusion of novel H-bonding solvent. Despite the diverse structural effects, the least destabilizing average substitution at each position was Ala, and not isosteric Ser.
Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, 32306-4300.