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Stoichiometry of a Cl − ‐translocating ATPase
Author(s) -
Gerencser George A.
Publication year - 1993
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(93)80391-7
Subject(s) - atp hydrolysis , stoichiometry , dephosphorylation , hydrolysis , chemistry , atpase , adenosine triphosphate , nucleotide , phosphate , intracellular , phosphorylation , chromatography , biochemistry , enzyme , phosphatase , organic chemistry , gene
It has been determined that Mg 2+ stimulates phosphorylation while Cl − stimulates dephosphorylation of the chloride pump during its reaction sequence. The Stoichiometry of ATP hydrolyzed to Cl − transported during a single cycle of the reaction sequence was ascertained. Intracellular concentrations of ATP, ADP and inorganic phosphate were determined and, coupled with an estimate of the standard free energy of hydrolysis for ATP, the operant free energy for ATP hydrolysis was calculated. Because the operating free energy of the pump is approximately one‐half the energy obtained from the total free energy of ATP hydrolysis, the only possible integral stoichiometries are one or, at the most, two net charges transported per cycle per ATP hydrolyzed.