English
 
User Manual Privacy Policy Disclaimer Contact us
  Advanced SearchBrowse

Item

ITEM ACTIONSEXPORT

Released

Journal Article

Water penetration profile at the protein-lipid interface in Na,K-ATPase membranes.

MPS-Authors
/persons/resource/persons15495

Marsh,  D.
Department of NMR Based Structural Biology, MPI for biophysical chemistry, Max Planck Society;

Fulltext (public)

2065830.pdf
(Publisher version), 591KB

Supplementary Material (public)

2065830_Suppl_1.pdf
(Supplementary material), 101KB

2065830_Suppl_2.pdf
(Supplementary material), 692KB

Citation

Bartucci, R., Guzzi, R., Esmann, M., & Marsh, D. (2014). Water penetration profile at the protein-lipid interface in Na,K-ATPase membranes. Biophysical Journal, 107(6), 1375-1382. doi:10.1016/j.bpj.2014.07.057.


Cite as: http://hdl.handle.net/11858/00-001M-0000-0024-0566-0
Abstract
The affinity of ionized fatty acids for the Na,K-ATPase is used to determine the transmembrane profile of water penetration at the protein-lipid interface. The standardized intensity of the electron spin echo envelope modulation (ESEEM) from 2H-hyperfine interaction with D2O is determined for stearic acid, n-SASL, spin-labeled systematically at the C-n atoms throughout the chain. In both native Na,K-ATPase membranes from shark salt gland and bilayers of the extracted membrane lipids, the D2O-ESEEM intensities of fully charged n-SASL decrease progressively with position down the fatty acid chain toward the terminal methyl group. Whereas the D2O intensities decrease sharply at the n = 9 position in the lipid bilayers, a much broader transition region in the range n = 6 to 10 is found with Na,K-ATPase membranes. Correction for the bilayer population in the membranes yields the intrinsic D2O-intensity profile at the protein-lipid interface. For positions at either end of the chains, the D2O concentrations at the protein interface are greater than in the lipid bilayer, and the positional profile is much broader. This reveals the higher polarity, and consequently higher intramembrane water concentration, at the protein-lipid interface. In particular, there is a significant water concentration adjacent to the protein at the membrane midplane, unlike the situation in the bilayer regions of this cholesterol-rich membrane. Experiments with protonated fatty acid and phosphatidylcholine spin labels, both of which have a considerably lower affinity for the Na,K-ATPase, confirm these results.