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Crystal structure of sulfolobus tokodaii sua5 complexed with L ‐threonine and AMPPNP
Author(s) -
Kuratani Mitsuo,
Kasai Takuma,
Akasaka Ryogo,
Higashijima Kyoko,
Terada Takaho,
Kigawa Takanori,
Shinkai Akeo,
Bessho Yoshitaka,
Yokoyama Shigeyuki
Publication year - 2011
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.23026
Subject(s) - threonine , serine , stereochemistry , crystal structure , biology , crystallography , chemistry , biochemistry , phosphorylation
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 K d values of Sua5 for L ‐threonine and L ‐serine are 9.3 μ M and 2.6 m M , respectively. We determined the crystal structure of S. tokodaii Sua5, complexed with AMPPNP and L ‐threonine, at 1.8 Å 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. Proteins 2011. © 2011 Wiley‐Liss, Inc.