The Molecular Organization of Membranes

Studies on the transverse localization of lysophospholipase in bovine liver microsomes using proteolytic enzymes

“…In fact, the hydrolysis of lysophosphatidylchol~e was inhibited by the presence of phosphatidylcholine in a manner that could be explained most conveniently by dilution of the ly~phosphatidylcholine substrate in the plane of the lipid bilayer [3]. These characteristics, together with the observation reported in this paper that the enzyme could be solubilized from the membrane in a lipid-free state by sonication, would seem to classify the enzyme as a peripheral protein [4].…”

Extraction of erythrocyte membrane proteins by sulfhydryl inhibitors.

“…Every polypeptide is presumed to be bound to the membrane in a specific and characteristic fashion, and can be classified into two major categories termed peripheral and integral proteins (Singer and Nicolson 1972;Singer 1974). The peripheral proteins are composed of components 1, 2, and 5, which are selectively liberated when ghosts are placed in a low ionic strength, mild alkaline medium free of divalent cations (Signer and Nicolson 1972;Singer 1974;Steck 1974). The components 1 and 2 have been originally called spectrin because they are obtained from ghosts (Marchesi and Steers Jr. 1968) and amount to about 20 to 25% of the total membrane proteins (Singer 1974).…”

“…The peripheral proteins are composed of components 1, 2, and 5, which are selectively liberated when ghosts are placed in a low ionic strength, mild alkaline medium free of divalent cations (Signer and Nicolson 1972;Singer 1974;Steck 1974). The components 1 and 2 have been originally called spectrin because they are obtained from ghosts (Marchesi and Steers Jr. 1968) and amount to about 20 to 25% of the total membrane proteins (Singer 1974). Spectrin is considered to form a fibrous structure on the inner surface of the membrane and has been implicated in mainta ining the shape and integrity of the red cell (Marchesi and Steers Jr. 1968; Marchesi et al 1969).…”

“…The peripheral proteins are weakly bound to their respective membranes and are easily dissociated with mild treatments (Singer and Nicolson 1972;Singer 1974).…”

Ideas are becoming an endangered species.

“…To account for what I considered to be discrepancies with my model, I proposed that there had to be two kinds of membrane-associated proteins, integral proteins that had amphipathic molecular structures, and peripheral proteins, like cytochrome c, that resembled ordinary water-soluble proteins (Singer, 1971;Singer, 1974). I suggested that the peripheral proteins were attached to the membrane by specifically binding to the hydrophilic domains of certain integral proteins where these domains extended into the water phase.…”