4hyt

Publication Abstract from PubMed

The Na(+),K(+)-ATPase maintains electrochemical gradients for Na(+) and K(+) that are critical for animal cells. Cardiotonic steroids (CTSs), widely used in the clinic and recently assigned a role as endogenous regulators of intracellular processes, are highly specific inhibitors of the Na(+),K(+)-ATPase. Here we describe a crystal structure of the phosphorylated pig kidney Na(+),K(+)-ATPase in complex with the CTS representative ouabain, extending to 3.4 A resolution. The structure provides key details on CTS binding, revealing an extensive hydrogen bonding network formed by the beta-surface of the steroid core of ouabain and the side chains of alphaM1, alphaM2, and alphaM6. Furthermore, the structure reveals that cation transport site II is occupied by Mg(2+), and crystallographic studies indicate that Rb(+) and Mn(2+), but not Na(+), bind to this site. Comparison with the low-affinity [K2]E2-MgFx-ouabain structure [Ogawa et al. (2009) Proc Natl Acad Sci USA 106(33):13742-13747) shows that the CTS binding pocket of [Mg]E2P allows deep ouabain binding with possible long-range interactions between its polarized five-membered lactone ring and the Mg(2+). K(+) binding at the same site unwinds a turn of alphaM4, dragging residues Ile318-Val325 toward the cation site and thereby hindering deep ouabain binding. Thus, the structural data establish a basis for the interpretation of the biochemical evidence pointing at direct K(+)-Mg(2+) competition and explain the well-known antagonistic effect of K(+) on CTS binding.

Crystal structure of the high-affinity Na+,K+-ATPase-ouabain complex with Mg2+ bound in the cation binding site.,Laursen M, Yatime L, Nissen P, Fedosova NU Proc Natl Acad Sci U S A. 2013 Jul 2;110(27):10958-63. doi:, 10.1073/pnas.1222308110. Epub 2013 Jun 17. PMID:23776223^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.