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Conformational properties of 2′,5′ linked Rp ‐ and Sp ‐phosphorothioate oligoadenylates studied by circular dichroism and NMR
Author(s) -
Shimazu Masamitu,
Kawai Gohta,
Okutsu Tetsuo,
Shiozuka Kazuo,
Sawai Hiroaki
Publication year - 2002
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10282
Subject(s) - rnase p , chemistry , circular dichroism , stereochemistry , crystallography , proton nmr , ribonuclease , stacking , rna , biochemistry , organic chemistry , gene
2′,5′‐Linked oligoadenylates (2‐5A) are involved in the antiviral action of interferon. The 2‐5A binds and activates 2‐5A dependent RNase (RNase L), which degrades viral mRNA, resulting in the inhibition of protein synthesis. 2′,5′‐Linked phosphorothioate oligoadenylates with an Rp configuration bind to and activate the RNase L. On the other hand, 2′,5′ phosphorothioate oligoadenylate with an Sp configuration weakly binds to the RNase L and is devoid of the RNase L activation ability. Comparative circular dichroism (CD) and NMR studies are carried out to characterize the difference in properties between the two configurations of the 2′,5′ phosphorothioate oligoadenylates. 2′,5′ Rp ‐Phosphorothioate oligoadenylates showed CD spectra similar to those of the corresponding native 2′,5′ oligoadenylates, while the 2′,5′ Sp‐ phosphorothioate oligoadenylates exhibited a weaker CD band compared to the former two, indicating the weaker base‐stacking interaction of the 2′,5′ Sp‐ phosphorothioate oligoadenylates. The temperature‐dependent change in the CD revealed that 2′,5′ phosphorothioate oligoadenylates showed larger Δ H ° and Δ S ° values for the thermal transition of the conformation than the corresponding native 2′,5′ oligoadenylates. The NMR spectral assignment was accomplished by several NMR measuring techniques. The 2′‐H of the ribose ring linked to the 2′,5′ Sp‐ phosphorothioate showed a higher field chemical shift of the proton NMR than that linked to the corresponding 2′,5′ Rp ‐phosphorothioate. 2′,5′ Rp ‐ and Sp‐ phosphorothioate oligoadenylates possess a sugar conformation similar to that of the corresponding native 2′,5′ oligoadenylates. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 48–58, 2003