2c9m

Publication Abstract from PubMed

We present crystal structures of the calcium-free E2 state of the sarcoplasmic reticulum Ca2+ -ATPase, stabilized by the inhibitor thapsigargin and the ATP analog AMPPCP. The structures allow us to describe the ATP binding site in a modulatory mode uncoupled from the Asp351 phosphorylation site. The Glu439 side chain interacts with AMPPCP via an Mg2+ ion in accordance with previous Fe2+ -cleavage studies implicating this residue in the ATPase cycle and in magnesium binding. Functional data on Ca2+ mediated activation indicate that the crystallized state represents an initial stage of ATP modulated deprotonation of E2, preceding the binding of Ca2+ ions in the membrane from the cytoplasmic side. We propose a mechanism of Ca2+ activation of phosphorylation leading directly from the compact E2-ATP form to the Ca2E1-ATP state. In addition, a role of Glu439 in ATP modulation of other steps of the functional cycle is suggested.

Modulatory and catalytic modes of ATP binding by the calcium pump.,Jensen AM, Sorensen TL, Olesen C, Moller JV, Nissen P EMBO J. 2006 Jun 7;25(11):2305-14. Epub 2006 May 18. PMID:16710301^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.