title: Unraveling the Na,K-ATPase alpha(4) subunit assembling induced by large amounts of C(12)E(8) by means of small-angle X-ray scattering.
abstract: In the current work, we studied the effect of the nonionic detergent dodecyloctaethyleneglycol, C(12)E(8), on the structure and oligomeric form of the Na,K-ATPase membrane enzyme (sodium-potassium pump) in aqueous suspension, by means of small-angle X-ray scattering (SAXS). Samples composed of 2 mg/mL of Na,K-ATPase, extracted from rabbit kidney medulla, in the presence of a small amount of C(12)E(8) (0.005 mg/mL) and in larger concentrations ranging from 2.7 to 27 mg/mL did not present catalytic activity. Under this condition, an oligomerization of the alpha subunits is expected. SAXS data were analyzed by means of a global fitting procedure supposing that the scattering is due to two independent contributions: one coming from the enzyme and the other one from C(12)E(8) micelles. In the small detergent content (0.005 mg/mL), the SAXS results evidenced that Na,K-ATPase is associated into aggregates larger than (alphabeta)(2) form. When 2.7 mg/mL of C(12)E(8) is added, the data analysis revealed the presence of alpha(4) aggregates in the solution and some free micelles. Increasing the detergent amount up to 27 mg/mL does not disturb the alpha(4) aggregate: just more micelles of the same size and shape are proportionally formed in solution. We believe that our results shed light on a better understanding of how nonionic detergents induce subunit dissociation and reassembling to minimize the exposure of hydrophobic residues to the aqueous solvent.
authors: Instituto de Física da Universidade de São Paulo, Cx. Postal 66318, CEP 05315-970 - São Paulo, SP, Brazil. lbarbosa@if.usp.br
authors: Leandro Ramos Souza
authors: LR
authors: Barbosa
authors: Carolina Fortes
authors: CF
authors: Rigos
authors: Juliana Sakamoto
authors: JS
authors: Yoneda
authors: Rosangela
authors: R
authors: Itri
authors: Pietro
authors: P
authors: Ciancaglini
mesh_terms: D000818:Animals; D003902:Detergents / Q000737:chemistry*; D007679:Kidney Medulla / Q000201:enzymology; D008823:Micelles; D011092:Polyethylene Glycols / Q000737:chemistry*; D021122:Protein Subunits / Q000737:chemistry; D011817:Rabbits; D053838:Scattering, Small Angle; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000378:metabolism; D014961:X-Ray Diffraction
chemical_list: D003902:Detergents; D008823:Micelles; D021122:Protein Subunits; C017272:dodecyloctaethyleneglycol monoether; D011092:Polyethylene Glycols; D000254:Sodium-Potassium-Exchanging ATPase