Fluoroaluminate complexes are bifunctional analogues of phosphate in sarcoplasmic reticulum Ca(2+)-ATPase.

摘要: Abstract The mechanism of inhibition the sarcoplamc reticulum (SR) Ca(2+)-ATPase by fluoroaluminate complexes was investigated. First, AlF4- shown to bind Ca(2+)-free conformation enzyme a slow quasi-irreversible process. rate constants reaction are k+ = 16 x 10(3) M-1 s-1 and k- < 1.5 10(-3) s-1. We directly measured stoichiometry about 4.8 nmol bound/mg protein. Mg2+ necessary cofactor for with dissociation constant 3 mM. It demonstrated (Dupont, Y., Pougeois, R. (1983) FEBS Lett. 156, 93-98) that phosphorylation P(i) induced dehydration catalytic site. same process has been here occur upon binding either use Me2SO or demonstration an increase bound 2',3'-O-(2,4,6-trinitrocyclohexadienyldene)adenosine triphosphate fluorescence. Phosphorylation is inhibited AlF4-. Second, complex, presumably AlF4-, also Ca(2+)-bound in presence ADP stabilize E1.Ca2.ADP.AlFx complex. nucleotidic site shifted micromolar range. Ca2+ ions on external high affinity sites became occluded (ADP + AlFx). propose mimics ATPase stabilizes intermediate similar acyl-phosphate derivative; it acts as analogue gamma-phosphate ATP E1.[Ca2].ADP.AlF4 complex where occluded.