On the Accessibility of Essential Tyrosines in Isolated and Activated Chloroplast H+-ATPase
2014
Bickel-Sandkötter, Susanne | Esser, Kordula | Horbach, Martina
The addition of 7-chloro-4-nitrobenzofurazan to isolated and activated CF₁, creates a completely changed binding stoichiometry and subunit-distribution of bound modifier in contrast to the binding pattern in not-activated CF₁. The activation of CF₁, by dithiothreitol and heat results in the accessibility of three additional tyrosines in β-subunits and one additional tyro sine in α-subunits. Binding of pyridoxalphosphate to lysine in the active state suppresses the accessibility of the additional tyrosines, suggesting that PLP inactivates the ATPase by inducing a conformational change. Furthermore, two NBD -molecules are bound to γ-subunits when CF₁, is activated. These two molecules may be bound to sulfhydryl groups of cysteines which become accessible to NBD after activation.
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