3wcn

Crystal structure of the depentamerized mutant of selenocysteine synthase SelA

spinqualitylabelsall models 3wcn, resolution 3.35Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3wcn is a 2 chain structure with sequence from Aquifex aeolicus VF5. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 3.35Å Ligands: MSE, THJ Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function SELA_AQUAE Converts seryl-tRNA(Sec) to selenocysteinyl-tRNA(Sec) required for selenoprotein biosynthesis (By similarity). Publication Abstract from PubMed The 21st amino acid, selenocysteine (Sec), is incorporated translationally into proteins and is synthesized on its specific tRNA (tRNASec). In Bacteria, the selenocysteine synthase SelA converts Ser-tRNASec, formed by seryl-tRNA synthetase, to Sec-tRNASec. SelA, a member of the fold-type-I pyridoxal 5'-phosphate-dependent enzyme superfamily, has an exceptional homodecameric quaternary structure with a molecular mass of about 500kDa. Our previously determined crystal structures of Aquifex aeolicus SelA complexed with tRNASec revealed that the ring-shaped decamer is composed of pentamerized SelA dimers, with two SelA dimers arranged to collaboratively interact with one Ser-tRNASec. The SelA catalytic site is close to the dimer-dimer interface, but the significance of the dimer pentamerization in the catalytic site formation remained elusive. In the present study, we examined the quaternary interactions and demonstrated their importance for SelA activity by systematic mutagenesis. Furthermore, we determined the crystal structures of "depentamerized" SelA variants with mutations at the dimer-dimer interface that prevent pentamerization. These dimeric SelA variants formed a distorted and inactivated catalytic site and confirmed that the pentamer interactions are essential for productive catalytic site formation. Intriguingly, the conformation of the non-functional active site of dimeric SelA shares structural features with other fold-type-I pyridoxal 5'-phosphate-dependent enzymes with native dimer or tetramer (dimer-of-dimers) quaternary structures. Dimer-Dimer Interaction of the Bacterial Selenocysteine Synthase SelA Promotes Functional Active-Site Formation and Catalytic Specificity.,Itoh Y, Brocker MJ, Sekine SI, Soll D, Yokoyama S J Mol Biol. 2014 Jan 20. pii: S0022-2836(14)00022-9. doi:, 10.1016/j.jmb.2014.01.003. PMID:24456689 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Selenocysteine synthase

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