Molecular Insights into the Enigmatic Metabolic Regulator, SnRK1

Sucrose non-fermenting-1 (SNF1)-related kinase 1 (SnRK1) lies at the heart of metabolic homeostasis in plants and is crucial for normal development and response to stress. Evolutionarily related to SNF1 in yeast and AMP-activated kinase (AMPK) in mammals, SnRK1 acts protectively to maintain homeostasis in the face of fluctuations in energy status. Despite a conserved function, the structure and regulation of the plant kinase differ considerably from its relatively well-understood opisthokont orthologues. In this review, we highlight the known plant-specific modes of regulation involving SnRK1 together with new insights based on a 3D molecular model of the kinase. We also summarise how these differences from other orthologues may be specific adaptations to plant metabolism, and offer insights into possible avenues of future inquiry into this enigmatic enzyme. SnRK1 from plants is a central, enigmatic metabolic regulator that is functionally and evolutionarily related to SNF1 from yeast and AMPK from mammals. Recent advances have shown that both the subunit structure and regulation of plant SnRK1 differ considerably from those of its better-understood opisthokont orthologues. SnRK1 acts within complex signalling networks to maintain energy metabolism in plants. The distinct features and regulation, in relation to opisthokonts, likely enable SnRK1 to bring about responses specific to the demands of plant metabolism.