An extensive ion-pair/hydrogen-bond network contributes to the thermostability of the MutL ATPase domain from Aquifex aeolicus
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Updated: Jun 30, 2025

X-Ray Crystallography to Study the Oligomeric State Transition of the Thermotoga maritima M42 Aminopeptidase TmPep1050
Published on: May 13, 2020
Ayaka Shibuya1, Maki Yokote1, Atsushi Suzuki1
1Department of Biochemistry, Faculty of Medicine, Osaka Medical and Pharmaceutical University, 2-7 Daigaku-machi, Takatsuki, Osaka 569-8686, Japan.
Abstract:
Proteins from hyperthermophiles often contain a large number of ionic interactions. Close examination of the previously determined crystal structure of the ATPase domain of MutL from a hyperthermophile, Aquifex aeolicus, revealed that the domain contains a continuous ion-pair/hydrogen-bond network consisting of 11 charged amino acid residues on a β-sheet. Mutations were introduced to disrupt the network, showing that the more extensively the network was disrupted, the greater the thermostability of the protein was decreased. Based on urea denaturation analysis, a thermodynamic parameter, energy for the conformational stability, was evaluated, which indicated that amino acid residues in the network contributed additively to the protein stability. A continuous network rather than a cluster of isolated interactions would pay less entropic penalty upon fixing the side chains to make the same number of ion pairs/hydrogen bonds, which might contribute more favorably to the structural formation of thermostable proteins.
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