Nucleotide binding to noncatalytic sites is essential for ATP-dependent stimulation and ADP-dependent inactivation of the chloroplast ATP synthase |
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Authors: | Alexander N Malyan |
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Institution: | (1) Institute of Basic Biological Problems, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia |
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Abstract: | Light-dependent binding of labeled ADP and ATP to noncatalytic sites of chloroplast ATP synthase and the effect of light-exposed
thylakoid membrane preincubation with ADP or ATP on ATPase activity were studied. ADP binding during the preincubation was
shown to inactivate the chloroplast ATPase, whereas ATP binding caused its activation. The rate and equilibrium constants
of ATPase inactivation and activation were close to those of ADP and ATP binding to a noncatalytic site, with K
d values of 38 and 33 μM, respectively. It is suggested that ADP- or ATP-binding to one of the noncatalytic sites affects the
ATPase activity of chloroplast ATP synthase through a mechanism that modulates tightness of ADP binding to a catalytic site. |
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Keywords: | |
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