title: Protein stability and surface electrostatics: a charged relationship.
abstract: Engineering proteins to withstand a broad range of conditions continues to be a coveted objective, holding the potential to advance biomedicine, industry, and our understanding of disease. One way of achieving this goal lies in elucidating the underlying interactions that define protein stability. It has been shown that the hydrophobic effect, hydrogen bonding, and packing interactions between residues in the protein interior are dominant factors that define protein stability. The role of surface residues in protein stability has received much less attention. It has been believed that surface residues are not important for protein stability particularly because their interactions with the solvent should be similar in the native and unfolded states. In the case of surface charged residues, it was sometimes argued that solvent exposure meant that the high dielectric of the solvent will further decrease the strength of the charge-charge interactions. In this paper, we challenge the notion that the surface charged residues are not important for protein stability. We computationally redesigned sequences of five different proteins to optimize the surface charge-charge interactions. All redesigned proteins exhibited a significant increase in stability relative to their parent proteins, as experimentally determined by circular dichroism spectroscopy and differential scanning calorimetry. These results suggest that surface charge-charge interactions are important for protein stability and that rational optimization of charge-charge interactions on the protein surface can be a viable strategy for enhancing protein stability.
authors.affiliation: Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, USA.
authors.forename: Samantha S
authors.initials: SS
authors.lastname: Strickler
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Gribenko
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Gribenko
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Keiffer
authors.forename: Jessica
authors.initials: J
authors.lastname: Tomlinson
authors.forename: Tracey
authors.initials: T
authors.lastname: Reihle
authors.forename: Vakhtang V
authors.initials: VV
authors.lastname: Loladze
authors.forename: George I
authors.initials: GI
authors.lastname: Makhatadze
mesh_terms: D017766:Acid Anhydride Hydrolases / Q000737:chemistry / Q000235:genetics; D000595:Amino Acid Sequence; D043422:Carboxypeptidases A / Q000737:chemistry / Q000235:genetics; D004795:Enzyme Stability; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics; D017412:Ribonucleoprotein, U1 Small Nuclear / Q000737:chemistry / Q000235:genetics; D055672:Static Electricity; D013696:Temperature; D019063:Tenascin / Q000737:chemistry / Q000235:genetics; D013816:Thermodynamics; D025801:Ubiquitin / Q000737:chemistry / Q000235:genetics; D000097024:Acylphosphatase
chemical_list: D017766:Acid Anhydride Hydrolases; D043422:Carboxypeptidases A; D010446:Peptide Fragments; D011506:Proteins; D016601:RNA-Binding Proteins; D017412:Ribonucleoprotein, U1 Small Nuclear; D019063:Tenascin; D025801:Ubiquitin; D000097024:Acylphosphatase; C075339:U1A protein; C114731:tenascin fibronectin type III domain (1-92)