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Publication Abstract from PubMed

The hypermodified nucleoside N(6)-threonylcarbamoyladenosine resides at position 37 of tRNA molecules bearing U at position 36 and maintains translational fidelity in the three kingdoms of life. The N(6)-threonylcarbamoyl moiety is composed of L-threonine and bicarbonate, and its synthesis was genetically shown to require YrdC/Sua5. YrdC/Sua5 binds to tRNA and ATP. In this study, we analyzed the L-threonine-binding mode of Sua5 from the archaeon Sulfolobus tokodaii. Isothermal titration calorimetry measurements revealed that S. tokodaii Sua5 binds L-threonine more strongly than L-serine and glycine. The Kd values of Sua5 for L-threonine and L-serine are 9.3 muM and 2.6 mM, respectively. We determined the crystal structure of S. tokodaii Sua5, complexed with AMPPNP and L-threonine, at 1.8 A resolution. The L-threonine is bound next to AMPPNP in the same pocket of the N-terminal domain. Thr118 and two water molecules form hydrogen bonds with AMPPNP in a unique manner for adenine-specific recognition. The carboxyl group and the side-chain hydroxyl and methyl groups of L-threonine are buried deep in the pocket, whereas the amino group faces AMPPNP. The L-threonine is located in a suitable position to react together with ATP for the synthesis of N(6)-threonylcarbamoyladenosine.

Crystal structure of Sulfolobus tokodaii Sua5 complexed with L-threonine and AMPPNP.,Kuratani M, Kasai T, Akasaka R, Higashijima K, Terada T, Kigawa T, Shinkai A, Bessho Y, Yokoyama S Proteins. 2011 Jul;79(7):2065-75. doi: 10.1002/prot.23026. Epub 2011 May 2. PMID:21538543^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.