8dqj

Crystal structure of pyrrolysyl-tRNA synthetase from Methanomethylophilus alvus engineered for acridone amino acid (AST) bound to ATP and acridone

spinqualitylabelsall models 8dqj, resolution 1.54Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 8dqj is a 2 chain structure with sequence from Candidatus Methanomethylophilus alvus. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 1.54Å Ligands: AMP, ATP, GOL, MG, PEG, T7Q Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function A0A3G3IHP7_9ARCH Publication Abstract from PubMed A recently developed genetic code expansion (GCE) platform based on the pyrrolysine amino-acyl tRNA synthetase (PylRS)/tRNA(Pyl) pair from Methanomethylophilus alvus (Ma) has improved solubility and lower susceptibility to proteolysis compared with the homologous and commonly used Methanosarcina barkeri (Mb) and M. mazei (Mm) PylRS GCE platforms. We recently created two new Ma PylRS variants for the incorporation of the fluorescent amino acid, acridonyl-alanine (Acd), into proteins at amber codons: one based on "transplanting" active site mutations from an established high-efficiency Mb PylRS and one that was de novo selected from a library of mutants. Here, we present the crystal structures of these two Ma PylRS variants with Acd/ATP bound to understand why the "active site transplant" variant (Acd-AST) displayed 6-fold worse Acd incorporation efficiency than the de novo selected PylRS (called Acd-RS1). The structures reveal that the Acd-AST binding pocket is too small and binds the three-ring aromatic Acd in a distorted conformation, whereas the more spacious Acd-RS1 active site binds Acd in a relaxed, planar conformation stabilized by a network of solvent-mediated hydrogen bonds. The poor performance of the AST enzyme is ascribed to a shift in the Ma PylRS beta-sheet framework relative to that of the Mb enzyme. This illustrates a general reason why "active site transplantation" may not succeed in creating efficient Ma PylRSs for other noncanonical amino acids. This work also provides structural details that will help guide the development of future Ma PylRS/tRNA(Pyl) GCE systems via de novo selection or directed evolution methods. Structures of Methanomethylophilus alvus Pyrrolysine tRNA-Synthetases Support the Need for De Novo Selections When Altering the Substrate Specificity.,Gottfried-Lee I, Perona JJ, Karplus PA, Mehl RA, Cooley RB ACS Chem Biol. 2022 Nov 17. doi: 10.1021/acschembio.2c00640. PMID:36395426 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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