Fe2+ -catalyzed oxidative cleavages of Ca2+ -ATPase reveal novel features of its pumping mechanism.


We have analyzed the Fe2+ -catalyzed oxidative cleavages of Ca2+ -ATPase in the presence of Ca2+, with or without the ATP analog 5'-adenylyl-beta,gamma-imidodiphosphate (AMP-PNP) or in the presence of the inhibitor thapsigargin. To identify the positions of cleavages as precisely as possible, we have used previously identified proteinase K and tryptic fragments as a standard, advanced mass spectrometry techniques, as well as specific antibodies. A number of cleavages are similar to those described for Na+,K+ -ATPase or other P-type pumps and are expected on the basis of the putative Mg2+ binding residues near the phosphorylated Asp351 in E1 or E2P conformations. However, intriguing new features have also been observed. These include a Fe2+ site near M3, which cannot be due to the presence of histidine residues as it was postulated in the case of Na+,K+ -ATPase and H+,K+ -ATPase. This site could represent a Ca2+ binding zone between M1 and M3, preceding Ca2+ occlusion within M4, 5, 6, and 8. In addition, we present evidence that, in the non-crystalline state, the N- and P-domain may approach each other, at least temporarily, in the presence of Ca2+ (E1Ca2 conformation), whereas the presence of Mg.ATP stabilizes the N to P interaction (E1.Mg.ATP conformation).

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@article{Montigny2004Fe2O, title={Fe2+ -catalyzed oxidative cleavages of Ca2+ -ATPase reveal novel features of its pumping mechanism.}, author={C{\'e}dric Montigny and Christine Jaxel and Alla Shainskaya and Jo{\"{e}lle Vinh and Val{\'e}rie Labas and Jesper Vuust M\oller and Steven J. D. Karlish and Marc le Maire}, journal={The Journal of biological chemistry}, year={2004}, volume={279 42}, pages={43971-81} }