Send to

Choose Destination
PeerJ. 2017 Mar 14;5:e3087. doi: 10.7717/peerj.3087. eCollection 2017.

Computer modelling reveals new conformers of the ATP binding loop of Na+/K+-ATPase involved in the transphosphorylation process of the sodium pump.

Author information

Department of Biophysics, 2nd Faculty of Medicine, Charles University Prague, Prague, Czech Republic; Laboratory of Tissue Engineering, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
Department of Medical Chemistry and Clinical Biochemistry, 2nd Faculty of Medicine, Charles University Prague , Prague , Czech Republic.
Small Animal Clinic, Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Science , Brno , Czech Republic.
Institute of Biochemistry and Endocrinology, University of Giessen , Giessen , Germany.


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 ATP's terminal phosphate to its aspartyl-phosphorylation site. In order to get information for how the transfer of the γ-phosphate group of ATP to the Asp369 is achieved, analogous molecular modeling of the M4-M5 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+•ATP to any of these sites in the "open conformation" may not lead to phosphorylation of Asp369. Additional conformations of the cytoplasmic loop were found wobbling between "open conformation" <==> "semi-open conformation <==> "closed conformation" in the absence of 2Mg2+•ATP. The cytoplasmic loop's conformational change to the "semi-open conformation"-characterized by a hydrogen bond between Arg543 and Asp611-triggers by binding of 2Mg2+•ATP to a single ATP site and conversion to the "closed conformation" the phosphorylation of Asp369 in the P-domain, and hence the start of Na+/K+-activated ATP hydrolysis.


Hinge movement; M4M5 loop; Na+/K+-ATPase phosphorylation; Open and closed conformations

Conflict of interest statement

The authors declare there are no competing interests.

Supplemental Content

Full text links

Icon for PeerJ, Inc. Icon for PubMed Central
Loading ...
Support Center