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  • Title: 1H-NMR investigation of the interaction between RNase T1 and a novel substrate analog, 2'-deoxy-2'-fluoroguanylyl-(3'-5')uridine.
    Author: Shibata Y, Shimada I, Ikehara M, Miyazawa T, Inagaki F.
    Journal: FEBS Lett; 1988 Aug 01; 235(1-2):237-40. PubMed ID: 2841155.
    Abstract:
    The interaction between RNase T1 and a non-hydrolysable substrate analog, 2'-deoxy-2'-fluoroguanylyl-(3'-5')uridine (GfpU), was investigated using 1H-NMR spectroscopy. In the complex, the Gfp portion takes the syn form around the glycosidic bond and the 3'-endo form for the ribose moiety, similar to those found in 3'-GMP and 2'-deoxy-2'-fluoroguanosine 3'-monophosphate (Gfp). However, in contrast to the cases of these two inhibitors, the complex formation with GfpU at pH 6.0 was found to shift the His-40 C2 proton resonance of RNase T1 to high field as much as 1 ppm. At pH 6.0, this histidine residue appears to be unprotonated in the complex, but is protonated in the free enzyme (pKa of His-40 being 7.9). His-40, rather than Glu-58, is probably involved in the catalytic mechanism as a Lewis base, supporting the recent results from site-directed mutagenesis.
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