Characteristics of the Combination of Inhibitory Mg2+ and Azide with the F1 ATPase from Chloroplasts

Murataliev, M.B.; Milgrom, Y.M.; Boyer, P.D.

Авторы: Murataliev M.B., Milgrom Y.M., Boyer P.D.
Журнал: Biochemistry
Том: 30
Номер: 34
Год издания: 1991
Издательство: American Chemical Society
Местоположение издательства: United States
Первая страница: 8305
Последняя страница: 8310
DOI: 10.1021/bi00098a004
Аннотация: The interactions between ADP, Mg2+, and azide that result in the inhibition of the chloroplast F1 ATPase (CF1) have been explored further. The binding of the inhibitory Mg2+ with low Kd is shown to occur only when tightly bound ADP is present at a catalytic site. Either the tightly bound ADP forms part of the Mg2+-binding site or it induces conformational changes creating the high-affinity site for inhibitory Mg2+. Kinetic studies show that CF1 forms two catalytically inactive complexes with Mg2+. The first complex results from Mg2+ binding with a Kd for Mg2+ dissociation of about 10-15 μM, followed by a slow conversion to a complex with a Kd of about 4 μM. The rate-limiting step of the CF1 inactivation by Mg2+ is the initial Mg2+ binding. When medium Mg2+ is chelated with EDTA, the two complexes dissociate with half-times of about 1 and 7 min, respectively. Azide enhances the extent of Mg2+-dependent inactivation by increasing the affinity of the enzyme for Mg2+ 3-4 times and prevents the reactivation of both complexes of CF1 with ADP and Mg2+. This results from decreasing the rate of Mg2+ release; neither the rate of Mg2+ binding to CF1 nor the rate of isomerization of the first inactive complex to the more stable form is affected by azide. This suggests that the tight-binding site for the inhibitory azide requires prior binding of both ADP and Mg2+.
Добавил в систему: Мунтян Мария Сергеевна

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Characteristics of the Combination of Inhibitory Mg2+ and Azide with the F1 ATPase from Chloroplastsстатья

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