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Rubisco Activase AAA? proteins CbbX
CO2-assimilation
Abstract:
The key photosynthetic, CO2-fixing enzyme
Rubisco forms inactivated complexes with its substrate
ribulose 1,5-bisphosphate (RuBP) and other sugar phosphate
inhibitors. The independently evolved AAA? proteins
Rubisco activase and CbbX harness energy from ATP
hydrolysis to remodel Rubisco complexes, facilitating
release of these inhibitors. Here, we discuss recent structural
and mechanistic advances towards the understanding
of protein-mediated Rubisco activation. Both activating
proteins appear to form ring-shaped hexameric arrangements
typical for AAA? ATPases in their functional form,
but display very different regulatory and biochemical
properties. Considering the thermolability of the plant
enzyme, an improved understanding of the mechanism for
Rubisco activation may help in developing heat-resistant
plants adapted to the challenge of global warming.
