Removal of surface charge-charge interactions from ubiquitin leaves the protein folded and very stable.
The contribution of solvent-exposed charged residues to protein stability was evaluated using ubiquitin as a model protein. We combined site-directed mutagenesis and specific chemical modifications to first replace all Arg residues with Lys, followed by carbomylation of Lys-amino groups. Under the conditions in which all carboxylic groups are protonated (at pH 2), the chemically modified protein is folded and very stable (DeltaG = 18 kJ/mol). These results indicate that surface charge-charge interactions are not an essential fundamental force for protein folding and stability.
Loladze
Vakhtang V
VV
Department of Biochemistry and Molecular Biology, Penn State University College of Medicine, Hershey, Pennsylvania 17033, USA.
Makhatadze
George I
GI
D002942:Circular Dichroism; D004305:Dose-Response Relationship, Drug; D005656:Fungal Proteins / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011522:Protons; D013816:Thermodynamics; D025801:Ubiquitin / Q000737:chemistry*; D014508:Urea / Q000494:pharmacology
D005656:Fungal Proteins; D011522:Protons; D025801:Ubiquitin; D014508:Urea