## 4 Examples of Evolutionary Conservation, Convergence and Divergence
Similarly, for MFSs, it is also possible to build a eukaryotic-prokaryotic \"core\" ensemble (353 residues) encompassing human, bovine, and rat GLUTs to _Plasmodium_ PfHT1 or _Escherichia coli_ Xyle [120], that despite the sequence identity around 30% has an RMSD as low as 2.7 \(\pm\) 1.2 A and extremely similar rocking-bundle movements embedded on each structure. In the case of PLGACs, the notable resemblance between eukaryotic neurotransmitter channels and their simple prokaryotic counterparts like _Gloebacter_ GLIC has turned the latter into the perfect model to study gating mechanisms. As often happens with ancestral protein machines, their function (channel opening/closing) requires complex motions (extracellular blooming coupled to tilting/twisting of intracellular pore-gating helices), which are both embedded in their pentameric ring-like architecture and extremely conserved across evolution [55; 121; 122]. Finally, another example of evolutionary selection acting on conformation could be behind mutational asymmetries in cancer, which tend to target signaling proteins. Global dynamics is a predictor of missense mutation pathogenicity [105; 123] and in cancer genes, it has been shown that mutations tend to cluster in specific functional spots and specifically hinge regions as determined via ENMs [104]. One striking example is the oncogene EGFR, which displays a puzzling tissue-specific mutational asymmetry. In brain glioblastoma (GBM), mutations are highly heterogenous but tend to cluster on the extracellular ligand-binding domain (ectodomain, ECD), even coexisting in the same tumor. In contrast, mutations in lung cancer concentrate in the intracellular kinase domain (KD), mostly focused on the catalytic cleft. This asymmetry results in intriguingly opposite responses to drugs binding to different KD conformers. Our ENM study of the ECD revealed that GBM mutations neatly cluster at hinge and interdomain regions, which control a large-scale conformational change of nearly 25 A between the closed-unbound and open-bound states. Further MD simulations revealed that GBM mutations favor spontaneous ECD opening following the lowest frequency modes, to acquire a transient conformation known to exist but never trapped experimentally. This ENM/MD intermediate was validated through structural, in vitro, and in vivo experiments [75; 124; 125], is shared by missense mutants from different ECD hotspots, and mimics the configuration of the most frequent change in GBM, the deletion EGFRVIII (Figure 1d). Specifically, the first tandem repeat of EGFR is \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Identity** & **Similarity** & **TM-Score** \\ \hline _NHE9—NapA_ & 22\% & 42\% & 0.82 \\ _Overlap NHE9—NapA NMA_ & 75\% & & \\ _Overlap NHE9—NapA X-ray transition_ & 82\% & & \\ \hline \hline \end{tabular} \({}^{\dagger}\)Adapted from Ref. [74].  
\end{table} 
Table 1: Sequence, structural and dynamical similarity between mammalian NHE9 and bacterial proton exchanger NapA \({}^{\dagger}\). deleted in EGFRvIII but rotates in missense mutations. The ultimate goal of this remarkable structural \"equivalence\" or \"convergence\" trick is to allosterically activate the KD in a specific way, distinct from that favored by lung cancer mutations, which explains their different sensitivity to drugs. Importantly, lung and brain cancer mutations are known to activate different signaling pathways [126], and our ENM-MD studies suggest that this is directly governed by the different conformational dynamics they favor. On one hand, this could be an example of convergent evolution of missense mutations and deletions to achieve a similar functional outcome, driven by positive selection of those variants that explore the soft modes opening the structure in a \"GBM-preferred\" mode.