%0 Generic
%A Rudbeck, Maria E.
%A R. A. Blomberg, Margareta
%A Barth, Andreas
%D 2013
%T Hydrolysis of the E2P Phosphoenzyme of the Ca2+-ATPase: A Theoretical Study
%U https://acs.figshare.com/articles/dataset/Hydrolysis_of_the_E2P_Phosphoenzyme_of_the_Ca_sup_2_sup_ATPase_A_Theoretical_Study/2389117
%R 10.1021/jp4049814.s001
%2 https://ndownloader.figshare.com/files/4028806
%K aspartyl phosphate oxygen approaches Lys 684
%K hydrolysis reaction proceeds
%K nucleophilic attack
%K Thr 625
%K phosphorylated residue Asp 351
%K optimized structure
%K Theoretical StudyDephosphorylation
%K bond formation
%K transition state
%K reactant state
%K Asp 351 oxygen
%K kcal
%K water oxygen
%K activation barrier
%K E 2P Phosphoenzyme
%K sarcoplasmic reticulum
%K protonated phosphate product
%K bond breakage
%K Glu 183
%K water molecule
%K residue Glu 183
%K nonreacting groups
%K E 2P phosphoenzyme
%K phosphate group
%X Dephosphorylation of the E2P phosphoenzyme
intermediate of the
sarcoplasmic reticulum Ca2+-ATPase was studied using density
functional theory. The hydrolysis reaction proceeds via a nucleophilic
attack on the phosphorylated residue Asp351 by a water molecule, which
is positioned by the nearby residue Glu183 acting as a base. The activation
barrier was calculated to be 14.3 kcal/mol, which agrees well with
values of 15–17 kcal/mol derived from experimentally observed
rates. The optimized structure of the transition state reveals considerable
bond breakage between phosphorus and the Asp351 oxygen (distance 2.19 Å)
and little bond formation to the attacking water oxygen (distance
2.26 Å). Upon formation of the singly protonated phosphate product,
Glu183 becomes protonated. The bridging aspartyl phosphate oxygen
approaches Lys684 progressively when proceeding from the reactant
state (distance 1.94 Å) via the transition state (1.78 Å)
to the product state (1.58 Å). This stabilizes the negative charge
that develops on the leaving group. The reaction was calculated to
be slightly endergonic (+0.9 kcal/mol) and therefore reversible, in
line with experimental findings. It is catalyzed by a preorganized
active site with little movement of the nonreacting groups except
for a rotation of Thr625 toward the phosphate group.
%I ACS Publications