Data for: Viral receptor-binding protein evolves new function through mutations that cause trimer instability and functional heterogeneity

When proteins evolve new activity, a concomitant decrease in stability is
often observed because the mutations that confer new activity can
destabilize the native fold. In the conventional model of protein
evolution, reduced stability is considered a purely deleterious cost of
molecular innovation because unstable proteins are prone to aggregation
and are sensitive to environmental stressors. However, recent work has
revealed that non-native, often unstable protein conformations play an
important role in mediating evolutionary transitions, raising the question
of whether instability can itself potentiate the evolution of new
activity. We explored this question in a bacteriophage receptor binding
protein (RBP) during host-range evolution. We studied the properties of
the RBP of bacteriophage  before and after host-range evolution
and demonstrated that the evolved protein is relatively unstable and may
exist in multiple conformations with unique receptor preferences. Through
a combination of structural modeling and in vitro oligomeric state
analysis, we found that the instability arises from mutations that
interfere with trimer formation. This study raises the intriguing
possibility that protein instability might play a previously unrecognized
role in mediating host-range expansions in viruses.