The chloroplast ATP synthase features the characteristic redox regulation machinery.

SIGNIFICANCE: Regulation of the activity of the chloroplast ATP synthase is largely accomplished by the chloroplast thioredoxin system, the main redox regulation system in chloroplasts, which is directly coupled to the photosynthetic reaction. We review the current understanding of the redox regulation system of the chloroplast ATP synthase. RECENT ADVANCES: The thioredoxin-targeted portion of the ATP synthase consists of two cysteines located on the central axis subunit γ. The redox state of these two cysteines is under the influence of chloroplast thioredoxin, which directly controls rotation during catalysis by inducing a conformational change in this subunit. The molecular mechanism of redox regulation of the chloroplast ATP synthase has recently been determined. CRITICAL ISSUES: Regulation of the activity of the chloroplast ATP synthase is critical in driving efficiency into the ATP synthesis reaction in chloroplasts. FUTURE DIRECTIONS: The molecular architecture of the chloroplast ATP synthase, which confers redox regulatory properties requires further investigation, in light of the molecular structure of the enzyme complex as well as the physiological significance of the regulation system.