Biological membrane structure, I. The protein crystal model for membranes.

A geometric model for the arrangement of phospholipid and protein in biological membrane systems has been proposed. The essential principle underlying this model is that when membrane proteins polymerize, the points of contact between proteins are few, and cavities lined with predominantly nonpolar amino acids are formed. Phospholipid molecules become oriented with the fatty chains inserted into the cavities while the polar heads remain on the surface of the membrane. This orientation applies to both faces of the membrane continuum. All the lipid known to be present in membranes can be accommodated in this manner. The body of evidence supporting this model has been presented.