Effects of phospholipases C and D on ordering of channel proteins in the mitochondrial outer membrane

The effects of phospholipases C and D on the state of order of the channels in the outer membranes of Neurospora mitochondria have been investigated by negative-stain electron microscopy and optical diffraction. Unlike the situation with phospholipase A2, treatment of the isolated membranes with phospholipase C or D does not induce crystallization of the channels in the membrane plane. Furthermore, treatment of already-formed periodic arrays of outer membrane channels with either phospholipase C or D causes loss of long-range order in the arrays. The latter result suggests that zwitterionic phospholipids may play an important role in stabilizing the periodic arrays of the channel-forming protein in this membrane.