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 (ΔG = 18 kJ/mol). These results indicate that surface charge–charge interactions are not an essential fundamental force for protein folding and stability.

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