The first 3′:5′-cyclic nucleotide–amino acid complex:L-His–cIMP

Abstract

In the crystal structure of the L-His–cIMP complex,i.e.L-histidinium inosine 3′:5′-cyclic phosphate [systematic name: 5-(2-amino-2-carboxyethyl)-1H-imidazol-3-ium 7-hydroxy-2-oxo-6-(6-oxo-6,9-dihydro-1H-purin-9-yl)-4a,6,7,7a-tetrahydro-4H-1,3,5,2λ5-furo[3,2-d][1,3,2λ5]dioxaphosphinin-2-olate], C6H10N3O2+·C10H10N4O7P−, the Hoogsteen edge of the hypoxanthine (Hyp) base of cIMP and the Hyp face are engaged in specific amino acid–nucleotide (His...cIMP) recognition,i.e.by abutting edge-to-edge and by π–π stacking, respectively. The Watson–Crick edge of Hyp and the cIMP phosphate group play a role in nonspecific His...cIMP contacts. The interactions between the cIMP anions (anti/C3′–endo/trans–gauche/chair conformers) are realized mainly between riboses and phosphate groups. The results for this L-His–cIMP complex, compared with those for the previously reported solvated L-His–IMP crystal structure, indicate a different nature of amino acid–nucleotide recognition and interactions upon the 3′:5′-cyclization of the nucleotide phosphate group.