Figure 4.

The average fitness of co-selected protein pairs as a function of the number of shared contacts between the pairs. Populations of size 1,000 were equilibrated for N generations under a co-selection regime (see methods). The fitness values were averaged across all structure pairs with the same number of shared contacts. Since there was no correlation between fitness of co-selected pairs and the designabilities of the structures in the pair, the fitnesses shown here were averaged over all possible structure pairs regardless of designability.