E1/E2 type cation transport ATPases: Evidence for transient associations between protomers

E1/E2 type cation transport ATPases are known to exist in different conformeric states. Recent evidence characterizing these conformers in membrane is reviewed. A consensus view is proposed in which E2 conformers tend to form oligomeric complexes by lateral association between monomeric protomers and El conformers exhibit the opposite behaviour. It is suggested that transient associations between monomers during cation pump cycles may be a common feature of the ion translocation mechanism under physiological conditions.