This review will focus on the effect of non-bilayer lipids, or the pro
pensity for hexagonal II phase formation, on the activity of mycoplasm
a Mg2+-ATPase, mitochondrial ubiquinol-cytochrome c reductase and H+-A
TPase. The effect of several additives (bilayer stabilizers or promote
rs of H-II phase formation) on membrane enzyme activities is also disc
ussed.