Figure 2

Non-native interactions underpin the reverse hydrophobic effect. Representative unfolded conformations (right) based on PDB structures (left) were simulated using a coarse-grained continuum chain model that allows sequence-dependent non-native hydrophobic interactions [10]. (a) An unfolded conformation (right) of a double mutant of the Fyn SH3 domain (PDB 1shf) containing a non-native contact between positions 40 and 53 as implicated by DMC [10]. (b-d) Residue positions in red are known experimentally to contribute to the reverse hydrophobic effect [6, 8, 9]. Those in black or blue are their most likely unfolded-state non-native interacting partners in our simulations. (b) The H1P variant of bacterial immunity protein Im9 (PDB 1imq) [9], non-native contact Ile17-Val37. (c) Chemotactic protein CheY (PDB 3chy) [8], Phe14-Met85. (d) λ Cro repressor (PDB 5cro), which unfolds from a dimer to two monomer chains [6], Tyr26-Leu42 and Tyr26-Tyr51. Question marks in (b-d) emphasize that the predicted non-native interactions are yet to be tested by experiment.