@article {2024|2168,
	title = {The characterization of ancient Methanococcales malate dehydrogenases reveals that strong thermal stability prevents unfolding under intense γ-irradiation},
	journal = {Mol. Biol. Evol.},
	volume = {41},
	year = {2024},
	abstract = {<p>Malate dehydrogenases (MalDHs) (EC.1.1.1.37), which are involved in the conversion of oxaloacetate to pyruvate in the tricarboxylic acid cycle, are a relevant model for the study of enzyme evolution and adaptation. Likewise, a recent study showed that Methanococcales, a major lineage of Archaea, is a good model to study the molecular processes of proteome thermoadaptation in prokaryotes. Here, we use ancestral sequence reconstruction and paleoenzymology to characterize both ancient and extant MalDHs. We observe a good correlation between inferred optimal growth temperatures and experimental optimal temperatures for activity (A-Topt). In particular, we show that the MalDH present in the ancestor of Methanococcales was hyperthermostable and had an A-Topt of 80 \&deg;C, consistent with a hyperthermophilic lifestyle. This ancestor gave rise to two lineages with different thermal constraints: one remained hyperthermophilic, while the other underwent several independent adaptations to colder environments. Surprisingly, the enzymes of the first lineage have retained a thermoresistant behavior (i.e. strong thermostability and high A-Topt), whereas the ancestor of the second lineage shows a strong thermostability, but a reduced A-Topt. Using mutants, we mimic the adaptation trajectory toward mesophily and show that it is possible to significantly reduce the A-Topt without altering the thermostability of the enzyme by introducing a few mutations. Finally, we reveal an unexpected link between thermostability and the ability to resist γ-irradiation-induced unfolding.</p>
},
	keywords = {ancestral sequence reconstruction, COaLA evolutionary model, extremophiles, irradiation, reactive oxygen species, thermal adaptation},
	author = {Madern, Dominique and Halgand, Fr{\'e}d{\'e}ric and Hou{\'e}e-Levin, Chantal and Dufour, Anne-B{\'e}atrice and Coquille, Sandrine and Ansanay-Alex, Salom{\'e} and S Sacquin-Mora and Brochier-Armanet, C{\'e}line}
}
