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Charge interactions can dominate the dimensions of intrinsically disordered proteins

2010; National Academy of Sciences; Volume: 107; Issue: 33 Linguagem: Inglês

10.1073/pnas.1001743107

1091-6490

Sonja Müller-Späth, Andrea Soranno, Verena Hirschfeld, Hagen Hofmann, Stefan Rüegger, Luc Reymond, Daniel Nettels, Benjamin Schuler,

Enzyme Structure and Function

Many eukaryotic proteins are disordered under physiological conditions, and fold into ordered structures only on binding to their cellular targets. Such intrinsically disordered proteins (IDPs) often contain a large fraction of charged amino acids. Here, we use single-molecule Förster resonance energy transfer to investigate the influence of charged residues on the dimensions of unfolded and intrinsically disordered proteins. We find that, in contrast to the compact unfolded conformations that have been observed for many proteins at low denaturant concentration, IDPs can exhibit a prominent expansion at low ionic strength that correlates with their net charge. Charge-balanced polypeptides, however, can exhibit an additional collapse at low ionic strength, as predicted by polyampholyte theory from the attraction between opposite charges in the chain. The pronounced effect of charges on the dimensions of unfolded proteins has important implications for the cellular functions of IDPs.