3U1H

Crystal structure of IPMDH from the last common ancestor of Bacillus

3U1H の概要

• エントリーDOI: 10.2210/pdb3u1h/pdb
• 分子名称: 3-isopropylmalate dehydrogenase (2 entities in total)
• 機能のキーワード: isocitrate/isopropylmalate dehydrogenase-like fold, oxidoreductase
• 由来する生物種: Bacillus sp.
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 85186.57

構造登録者

Haaning, S.,Hobbs, J.K.,Monk, C.R.,Arcus, V.L. (登録日: 2011-09-29, 公開日: 2011-11-02, 最終更新日: 2023-11-01)

主引用文献

Hobbs, J.K.,Shepherd, C.,Saul, D.J.,Demetras, N.J.,Haaning, S.,Monk, C.R.,Daniel, R.M.,Arcus, V.L.
On the Origin and Evolution of Thermophily: Reconstruction of Functional Precambrian Enzymes from Ancestors of Bacillus
MOL.BIOL.EVOL., 2011

PubMed Abstract: Thermophily is thought to be a primitive trait, characteristic of early forms of life on Earth, that has been gradually lost over evolutionary time. The genus Bacillus provides an ideal model for studying the evolution of thermophily as it is an ancient taxon and its contemporary species inhabit a range of thermal environments. The thermostability of reconstructed ancestral proteins has been used as a proxy for ancient thermal adaptation. The reconstruction of ancestral "enzymes" has the added advantages of demonstrable activity, which acts as an internal control for accurate inference, and providing insights into the evolution of enzymatic catalysis. Here, we report the reconstruction of the structurally complex core metabolic enzyme LeuB (3-isopropylmalate dehydrogenase, E. C. 1.1.1.85) from the last common ancestor (LCA) of Bacillus using both maximum likelihood (ML) and Bayesian inference. ML LeuB from the LCA of Bacillus shares only 76% sequence identity with its closest contemporary homolog, yet it is fully functional, thermophilic, and exhibits high values for k(cat), k(cat)/K(M), and ΔG(‡) for unfolding. The Bayesian version of this enzyme is also thermophilic but exhibits anomalous catalytic kinetics. We have determined the 3D structure of the ML enzyme and found that it is more closely aligned with LeuB from deeply branching bacteria, such as Thermotoga maritima, than contemporary Bacillus species. To investigate the evolution of thermophily, three descendents of LeuB from the LCA of Bacillus were also reconstructed. They reveal a fluctuating trend in thermal evolution, with a temporal adaptation toward mesophily followed by a more recent return to thermophily. Structural analysis suggests that the determinants of thermophily in LeuB from the LCA of Bacillus and the most recent ancestor are distinct and that thermophily has arisen in this genus at least twice via independent evolutionary paths. Our results add significant fluctuations to the broad trend in thermal adaptation previously proposed and demonstrate that thermophily is not exclusively a primitive trait, as it can be readily gained as well as lost. Our findings also demonstrate that reconstruction of complex functional Precambrian enzymes is possible and can provide empirical access to the evolution of ancient phenotypes and metabolisms.

PubMed: 21998276
DOI: 10.1093/molbev/msr253

実験手法

X-RAY DIFFRACTION (2.8 Å)