University of Turku
Supervisor: Reijo Lahti
Membrane pyrophosphatases (PPases) are integral membrane proteins that couple hydrolysis of pyrophosphate (PPi) to transmembrane transport of H+ or Na+ ions. Structurally, membrane PPases are among the simplest primary transporters and thus an attractive model system to study ion transport mechanisms. Membrane PPases are found in most plants, many bacteria and archaea. H+-transporting PPases appear to provide the host organism with essential energy reserves during stress and low energy conditions. In contrast, physiological function of recently discovered Na+-transporting PPases (Malinen et al. 2007) remains unknown. In this research plan, I suggest to (I) decipher the pathways of molecular evolution leading to differing ion transport specificities in membrane PPase subfamilies, (II) define kinetically the mechanism that couples PPi hydrolysis to ion transport, (III) explore the effect of membrane PPase expression on plant physiology and survival during stress, and (IV) examine the physiological role and interplay of Na+- and H+-pumping PPases in the archaeon Methanosarcina mazei.