First-Step Mutations for Adaptation at Elevated Temperature Increase Capsid Stability in a Virus
Figure 1
Mutational pathways to a novel function when function and stability trade-off.
(A) Dashed line: mutation 1 on the ancestral background confers increase in novel function, but stability is decreased. If trade-off is severe, fitness may decline. Mutation 2 is compensatory and increases both stability and fitness. Solid line: mutation 2 on the ancestor does not affect function or fitness and is, thus, neutral, but pre-adapts the protein by increasing stability. Mutation 1 on the background of 2 then increases function and fitness. (B) Elevated temperature selects for increased stability in the absence of selection for a novel function. The protein is now pre-adapted should selection for a novel function arise later.