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Interaction between the mitochondrial ATP synthetase and ATPase inhibitor protein
Author(s) -
Panchenko Maria V.,
Vinogradov Andrei D.
Publication year - 1985
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(85)80611-6
Subject(s) - inhibitor protein , chemistry , deprotonation , reagent , protonation , atpase , histidine , submitochondrial particle , biochemistry , stereochemistry , enzyme , organic chemistry , ion
The rate of mitochondrial ATPase inactivation by the naturally occurring inhibitor protein in the presence of saturating ATP and Mg 2+ at pH 8.0 depends hyperbolically on the amount of inhibitor added; the upper limit of an apparent first‐order constant for the inactivation process is 1.0 −1 at 25°C. A dramatic difference in the inactivation rate is observed when the protein inhibitor is added to the same assay system from either acidic (pH 4.8) or alkaline (pH 8.2) solutions. The slow reversible transition of the inhibitor from its rapidly reacting ‘acidic’ form to the slow reacting ‘alkaline’ form occurs when the solution of the protein inhibitor is subjected to a pH‐jump from 4.8 to 8.2 ( t ½ ~ 30 s at 25°C). The pH‐profile of the inhibitor active/inactive equilibrium suggests that a group with p K a ~ 6.5 is involved in the transition. Treatment of the inhibitor protein with a histidine‐specific reagent (e.g. diethyl pyrocarbonate) abolishes its inactivating effect on the ATPase activity. It is concluded that the protonation/deprotonation of the inhibitor protein followed by its slow conformational changes is the rate‐limiting step in the inhibitor‐ATP synthetase interaction.