... nitrogens of Glu40,Asn41, and Arg42, and OE1 or OE2 of Glu43, and thephosphate-binding site contains Glu56, Arg67, Arg71,His86, and Tyr87. In the exo-2¢,3¢-GCPT complex, O2¢ and O3¢ form hydrogen ... which is turned by 90° and sandwiched between His86 and Thr69 (Fig. 4C). Thesecond phosphate group of the trinucleotide is posi-tioned between Asp66–Thr69 and Arg34 NH1 and NH2, which are 3.2 ... A˚box, and centered at the geomet-rical center of the bound nucleotides. Molecules ofmononucleotides 2¢-GMP, 2¢,3¢-GCPT, 3¢-GMP, 3¢-CMP,3¢-UMP, and 3¢-AMP, dinucleotides GG, GA, GC, and GU, and...