12 research outputs found
Rape (Brassica chinensis L.) seed germination, seedling growth, and physiology in soil polluted with di-n-butyl phthalate and bis(2-ethylhexyl) phthalate
Endogenous and exogenous cardiac glycosides: their roles in hypertension, salt metabolism, and cell growth
Computer modelling reveals new conformers of the ATP binding loop of Na+/K+-ATPase involved in the transphosphorylation process of the sodium pump
Hydrolysis of ATP by Na+/K+-ATPase, a P-Type ATPase, catalyzing active Na+ and K+ transport through cellular membranes leads transiently to a phosphorylation of its catalytical α-subunit. Surprisingly, three-dimensional molecular structure analysis of P-type ATPases reveals that binding of ATP to the N-domain connected by a hinge to the P-domain is much too far away from the Asp369 to allow the transfer of ATPâs terminal phosphate to its aspartyl-phosphorylation site. In order to get information for how the transfer of the Îł-phosphate group of ATP to the Asp369 is achieved, analogous molecular modeling of the M4âM5 loop of ATPase was performed using the crystal data of Na+/K+-ATPase of different species. Analogous molecular modeling of the cytoplasmic loop between Thr338 and Ile760 of the α2-subunit of Na+/K+-ATPase and the analysis of distances between the ATP binding site and phosphorylation site revealed the existence of two ATP binding sites in the open conformation; the first one close to Phe475 in the N-domain, the other one close to Asp369 in the P-domain. However, binding of Mg2+âąATP to any of these sites in the âopen conformationâ may not lead to phosphorylation of Asp369. Additional conformations of the cytoplasmic loop were found wobbling between âopen conformationâ  âsemi-open conformation  âclosed conformationâ in the absence of 2Mg2+âąATP. The cytoplasmic loopâs conformational change to the âsemi-open conformationââcharacterized by a hydrogen bond between Arg543 and Asp611âtriggers by binding of 2Mg2+âąATP to a single ATP site and conversion to the âclosed conformationâ the phosphorylation of Asp369 in the P-domain, and hence the start of Na+/K+-activated ATP hydrolysis