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bioRxiv · 10.1101/2022.10.25.513693

The rugged DNA-binding sequence-fitness landscape of the LacI/GalR Family is a product of asymmetry in the operator:repressor complex

Meger, A. T.·Spence, M. A.·Sandhu, M.·Jackson, C. J.·Raman, S.
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Abstract

How a proteins function influences the shape of its fitness landscape, smooth or rugged, is a fundamental question in evolutionary biochemistry. Smooth landscapes arise when incremental mutational steps lead to a progressive change in function, as commonly seen in enzymes and binding proteins. On the other hand, rugged landscapes are poorly understood because of the inherent unpredictability of how sequence changes affect function. Here, we experimentally characterize the entire sequence phylogeny, comprising 1158 extant and ancestral sequences, of the DNA-binding domain (DBD) of the LacI/GalR transcriptional repressor family. Our analysis revealed an extremely rugged landscape with rapid switching of specificity even between adjacent nodes. Further, the ruggedness arises due to the necessity of the repressor to simultaneously evolve specificity for asymmetric operators and disfavors potentially adverse regulatory crosstalk. Our study provides fundamental insight into evolutionary, molecular, and biophysical rules of genetic regulation through the lens of fitness landscapes.

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Meger, A. T., Spence, M. A., Sandhu, M., Jackson, C. J., Raman, S.. 2022-10-25. The rugged DNA-binding sequence-fitness landscape of the LacI/GalR Family is a product of asymmetry in the operator:repressor complex. https://doi.org/10.1101/2022.10.25.513693

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