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Biophys J. 2019 Sep 3;117(5):930-937. doi: 10.1016/j.bpj.2019.07.019. Epub 2019 Jul 19.

Temperature-Dependent Interactions Explain Normal and Inverted Solubility in a γD-Crystallin Mutant.

Author information

1
School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland.
2
Department of Chemistry, Maynooth University, Maynooth, Ireland.
3
Department of Chemistry, Duke University, Durham, North Carolina.
4
Department of Chemistry, Maynooth University, Maynooth, Ireland. Electronic address: jennifer.mcmanus@mu.ie.

Abstract

Protein crystal production is a major bottleneck in the structural characterization of proteins. To advance beyond large-scale screening, rational strategies for protein crystallization are crucial. Understanding how chemical anisotropy (or patchiness) of the protein surface, due to the variety of amino-acid side chains in contact with solvent, contributes to protein-protein contact formation in the crystal lattice is a major obstacle to predicting and optimizing crystallization. The relative scarcity of sophisticated theoretical models that include sufficient detail to link collective behavior, captured in protein phase diagrams, and molecular-level details, determined from high-resolution structural information, is a further barrier. Here, we present two crystal structures for the P23T + R36S mutant of γD-crystallin, each with opposite solubility behavior: one melts when heated, the other when cooled. When combined with the protein phase diagram and a tailored patchy particle model, we show that a single temperature-dependent interaction is sufficient to stabilize the inverted solubility crystal. This contact, at the P23T substitution site, relates to a genetic cataract and reveals at a molecular level the origin of the lowered and retrograde solubility of the protein. Our results show that the approach employed here may present a productive strategy for the rationalization of protein crystallization.

PMID:
31422822
PMCID:
PMC6731388
[Available on 2020-09-03]
DOI:
10.1016/j.bpj.2019.07.019

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