Single-mutation fitness landscapes for an enzyme on multiple substrates reveal specificity is globally encoded
نویسندگان
چکیده
Our lack of total understanding of the intricacies of how enzymes behave has constrained our ability to robustly engineer substrate specificity. Furthermore, the mechanisms of natural evolution leading to improved or novel substrate specificities are not wholly defined. Here we generate near-comprehensive single-mutation fitness landscapes comprising >96.3% of all possible single nonsynonymous mutations for hydrolysis activity of an amidase expressed in E. coli with three different substrates. For all three selections, we find that the distribution of beneficial mutations can be described as exponential, supporting a current hypothesis for adaptive molecular evolution. Beneficial mutations in one selection have essentially no correlation with fitness for other selections and are dispersed throughout the protein sequence and structure. Our results further demonstrate the dependence of local fitness landscapes on substrate identity and provide an example of globally distributed sequence-specificity determinants for an enzyme.
منابع مشابه
Specificity Effects of Amino Acid Substitutions in Promiscuous Hydrolases: Context‐Dependence of Catalytic Residue Contributions to Local Fitness Landscapes in Nearby Sequence Space
Catalytic promiscuity can facilitate evolution of enzyme functions-a multifunctional catalyst may act as a springboard for efficient functional adaptation. We test the effect of single mutations on multiple activities in two groups of promiscuous AP superfamily members to probe this hypothesis. We quantify the effect of site-saturating mutagenesis of an analogous, nucleophile-flanking residue i...
متن کاملThe rank ordering of genotypic fitness values predicts genetic constraint on natural selection on landscapes lacking sign epistasis.
Sewall Wright's genotypic fitness landscape makes explicit one mechanism by which epistasis for fitness can constrain evolution by natural selection. Wright distinguished between landscapes possessing multiple fitness peaks and those with only a single peak and emphasized that the former class imposes substantially greater constraint on natural selection. Here I present novel formalism that mor...
متن کاملThe Role of Highly Conserved Tryptophan in the Sixth Conserved Region at Substrate Specificity of α- amylase
Early in this study, an α-Amylase from Bacillus megaterium WHO (BMW) was isolated from hot springs of Ramsar (North of Iran), and its gene was cloned in E.coli. Based on its conserved sequence regions and substrate specificity, it was classified as intermediary group enzymes with the specificity of oligo-1,6-glucosidase and neopullulanase subfamilies. In the sixth conserved re...
متن کاملMultidimensional epistasis and fitness landscapes in enzyme evolution.
The conventional analysis of enzyme evolution is to regard one single salient feature as a measure of fitness, expressed in a milieu exposing the possible selective advantage at a given time and location. Given that a single protein may serve more than one function, fitness should be assessed in several dimensions. In the present study we have explored individual mutational steps leading to a t...
متن کاملEpistasis and Shapes of Fitness Landscapes
The relationship between the shape of a fitness landscape and the underlying gene interactions, or epistasis, has been extensively studied in the two-locus case. Gene interactions among multiple loci are usually reduced to two-way interactions. We present a geometric theory of shapes of fitness landscapes for multiple loci. A central concept is the genotope, which is the convex hull of all poss...
متن کامل