Abstract
Epistasis is a major determinant in the emergence of novel protein function. In allosteric proteins, direct interactions between inducer-binding mutations propagate through the allosteric network, manifesting as epistasis at the level of biological function. Elucidating this relationship between local interactions and their global effects is essential to understanding evolution of allosteric proteins. We integrate computational design, structural and biophysical analysis to characterize the emergence of novel inducer specificity in an allosteric transcription factor. Adaptive landscapes of different inducers of the designed mutant show that a few strong epistatic interactions constrain the number of viable sequence pathways, revealing ridges in the fitness landscape leading to new specificity. The structure of the designed mutant shows that a striking change in inducer orientation still retains allosteric function. Comparing biophysical and functional properties suggests a nonlinear relationship between inducer binding affinity and allostery. Our results highlight the functional and evolutionary complexity of allosteric proteins.
Highlights
Epistasis is a major determinant in the emergence of novel protein function
As allosteric proteins evolve toward new function, such as orthologs in different organisms, their inducer specificity changes to adapt to the new environment[25]
By reconstructing all sequence pathways connecting the two states, we found that nonspecific epistatic interactions of two distinct sets of amino acids separately drive loss of naringenin response while increasing resveratrol response
Summary
Direct interactions between inducer-binding mutations propagate through the allosteric network, manifesting as epistasis at the level of biological function. Structural and biophysical analysis to characterize the emergence of novel inducer specificity in an allosteric transcription factor. Mutations in the binding pocket that trigger the allosteric network have the potential to create new nonspecific epistatic interactions at the level of protein function, beyond the physical interactions commonly seen in specific epistasis. For an allosteric transcription factor (aTF), a function is the outcome of affinity for the inducer ligand, affinity for DNA, and allosteric changes that accompany binding to the ligand Each of these parameters will have its own fitness function mapped over the same sequence space, creating unique fitness landscapes. Our approach provides a general conceptual and methodological framework to investigate epistasis in transcription factors
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
