Figure 1

Example of a 2D dimer. A) Low selective pressure for dimerization: δ = 0.04 (i.e., only sequences that lead to a protein fraction of at least 4% engaged in the functional dimer are viable). Amino acids are colored according to the mean sequence in the steady state (hydrophobic: dark; polar: light). B) The same dimer under a moderate selective pressure: δ = 0.1 This leads to a more hydrophobic interface. C) The same dimer with δ = 0.2. D) The neutral network for one of the protein partners when δ = 0.04. Black dots represent viable monomer sequences; red dots represent sequences that survive under the dimerization condition. Connections between sequences are omitted for clarity. The radial position of each sequence reflects its distance from an arbitrary center (the most populated sequence when δ = 0). E) Idem, δ = 0.1. F) Idem, δ = 0.2.