6ei8 | pdb_00006ei8
Crystal structure of human tRNA-dihydrouridine (20) synthase dsRBD F359A mutant
Structural highlights
Function[DUS2L_HUMAN] Dihydrouridine synthase. Catalyzes the synthesis of dihydrouridine, a modified base found in the D-loop of most tRNAs. Negatively regulates the activation of EIF2AK2/PKR.[1] [2] Publication Abstract from PubMedThe double-stranded RNA-binding domain (dsRBD) is a broadly distributed domain among RNA-maturing enzymes. Although this domain recognizes dsRNA's structures via a conserved canonical structure adopting an alpha1-beta1beta2beta3-alpha2 topology, several dsRBDs can accommodate discrete structural extensions expanding further their functional repertoire. How these structural elements engage cooperative communications with the canonical structure and how they contribute to the dsRBD's overall folding are poorly understood. Here, we addressed these issues using the dsRBD of human dihydrouridine synthase-2 (hDus2) (hDus2-dsRBD) as a model. This dsRBD harbors N- and C-terminal extensions, the former being directly involved in the recognition of tRNA substrate of hDus2. These extensions engage residues that form a long-range hydrophobic network (LHN) outside the RNA-binding interface. We show by coarse-grain Brownian dynamics that the Nt-extension and its residues F359 and Y364 rigidify the major folding nucleus of the canonical structure via an indirect effect. hDus2-dsRBD unfolds following a two-state cooperative model, whereas both F359A and Y364A mutants, designed to destabilize this LHN, unfold irreversibly. Structural and computational analyses show that these mutants are unstable due to an increase in the dynamics of the two extensions favoring solvent exposure of alpha2-helix and weakening the main folding nucleus rigidity. This LHN appears essential for maintaining a thermodynamic stability of the overall system and eventually a functional conformation for tRNA recognition. Altogether, our findings suggest that functional adaptability of extended dsRBDs is promoted by a cooperative hydrophobic coupling between the extensions acting as effectors and the folding nucleus of the canonical structure. Conformational Stability Adaptation of a Double-Stranded RNA-Binding Domain to Transfer RNA Ligand.,Bou-Nader C, Pecqueur L, Barraud P, Fontecave M, Tisne C, Sacquin-Mora S, Hamdane D Biochemistry. 2019 May 10. doi: 10.1021/acs.biochem.9b00111. PMID:31045345[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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