Tang, Hong-Jin and Ruan, Li-Jun and Tian, Hai-Yan and Liang, Guang-Ping and Ye, Wen-Cai and Hughes, Eleri and Esmann, Mikael and Fedosova, Natalya U. and Chung, Tse-Yu and Tzen, Jason T. C. and Jiang, Ren-Wang and Middleton, David Andrew (2016) Novel stereoselective bufadienolides reveal new insights into the requirements for Na+, K+-ATPase inhibition by cardiotonic steroids. Scientific Reports, 2016 (6): 29155. ISSN 2045-2322
Full text not available from this repository.Abstract
Cardiotonic steroids (CTS) are clinically important drugs for the treatment of heart failure owing to their potent inhibition of cardiac Na+, K+-ATPase (NKA). Bufadienolides constitute one of the two major classes of CTS, but little is known about how they interact with NKA. We report a remarkable stereoselectivity of NKA inhibition by native 3β-hydroxy bufalin over the 3α-isomer, yet replacing the 3β-hydroxy group with larger polar groups in the same configuration enhances inhibitory potency. Binding of the two 13C-labelled glycosyl diastereomers to NKA were studied by solid-state NMR (SSNMR), which revealed interactions of the glucose group of the 3β- derivative with the inhibitory site, but much weaker interactions of the 3α- derivative with the enzyme. Molecular docking simulations suggest that the polar 3β-groups are closer to the hydrophilic amino acid residues in the entrance of the ligand-binding pocket than those with α-configuration. These first insights into the stereoselective inhibition of NKA by bufadienolides highlight the important role of the hydrophilic moieties at C3 for binding, and may explain why only 3β-hydroxylated bufadienolides are present as a toxic chemical defence in toad venom.