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The crystal structure of the first two winged-helix motifs of translation elongation factor SelB from Moorella thermoacetica has been determined at 1.1 Å resolution. Compared with the previous structure of the two domains in conjunction with winged-helix modules 3 and 4, the first winged-helix domain underwent a substantial conformational change during which the α-helical and β-sheet portions of the element opened up like a shell. This conformational rearrangement was elicited by a change in the orientation of Trp396, leading to the disclosure of a bona fide ligand-binding site in the direct vicinity of Trp396. Additionally, the C-terminal tail of the second domain followed a different path compared with the previous structure. It is conceivable that these conformational switches constitute part of the molecular mechanism that underlies the communication between the N-terminal part of SelB, which binds Sec-tRNASec and GTP, and the C-terminal part of the protein, which binds selenocysteine-insertion sequences.

Supporting information

PDB reference: WH1 and WH2 motifs of SelB, 2v9v, r2v9vsf


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