For the synthetases possessing the class IIa anticodon-binding domain (ProRS, ThrRS and GlyRS, with the exception of HisRS), the two anticodon bases 35 and 36 are sufficient to uniquely identify the cognate tRNA (GG for proline, GU for threonine, CC for glycine), because these amino acids occupy full codon groups. The structure of ProRSTT in complex with its cognate tRNA shows that these two bases specifically interact with the enzyme, whereas base 34, which can be any base, is stacked under base 33 and makes no interactions with the synthetase. This is in agreement with biochemical experiments which identify bases 35 and 36 as major tRNA identity elements. In contrast, class IIb synthetases (AspRS, AsnRS and LysRS) have a distinct anticodon-binding domain that specifically recognises all three anticodon bases. This again correlates with the requirements of the genetic code for cognate tRNA identification, as the class IIb amino acids occupy half codon groups.

A new crystal form of the complex between seryl-tRNA synthetase and tRNASer from Thermus thermophilus that diffracts to 2.8 A resolution

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Институт молекулярной биологии и генетики НАН Украины 252143, Киев, ул. Академика Заболотного, 150 Изучена реакционная способность остатков фосфорной кислоты тРНКг™ из Т. thermophilus, находящейся в комплексе с серил-тРНК синтетазой. Серил-тРНК синтетаза из Т. thermophilus защищает от модификации нитрозоэтилмочевиной фосфаты акцепторного, вариабельного и Т-стеблей, а также Т-петли.