Structural basis for the hyperthermostability of an archaeal glutaminase induced by post-translational succinimide formation

Balaram, H.; Dongre, A. V.; Das, S.; Bellur, A.; Kumar, S.; Chandrashekarmath, A.; Karmakar, T.; Balaram, P.; Balasubramanian, S.

doi:10.1101/2021.03.02.433506

bioRxiv · 10.1101/2021.03.02.433506

Structural basis for the hyperthermostability of an archaeal glutaminase induced by post-translational succinimide formation

Balaram, H.·Dongre, A. V.·Das, S.·Bellur, A.·Kumar, S.·Chandrashekarmath, A.·Karmakar, T.·Balaram, P.·Balasubramanian, S.

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Abstract

Stability of proteins from hyperthermophiles enabled by reduction of conformational flexibility is realized through various mechanisms. Presence of a stable, hydrolysis-resistant succinimide arising from cyclization of the side chains of aspartyl/asparaginyl residues with backbone amide -NH of the succeeding residue would restrain the torsion angle {Psi}. Here, we describe the crystal structure of Methanocaldococcus jannaschii glutamine amidotransferase (MjGATase) and address the mechanism of a succinimide-induced increased thermostability using molecular dynamics simulations. This study reveals the interplay of negatively charged electrostatic shield and n[->]{pi}* interactions in preventing succinimide hydrolysis. The stable succinimidyl residue induces formation of a conformational-lock, reducing protein flexibility. Protein destabilization upon replacement with the {Phi}-restricted prolyl residue highlights the specificity of the conformationally restrained succinimidyl residue in imparting hyperthermostability. The conservation of succinimide-forming tripeptide sequence (E(N/D)(E/D)) in a group of archaeal GATases suggests an adaptation of this otherwise detrimental post-translational modification as an inducer of thermostability.

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Balaram, H., Dongre, A. V., Das, S., Bellur, A., Kumar, S., Chandrashekarmath, A., Karmakar, T., Balaram, P., Balasubramanian, S.. 2021-03-02. Structural basis for the hyperthermostability of an archaeal glutaminase induced by post-translational succinimide formation. https://doi.org/10.1101/2021.03.02.433506

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