FIGURE 1.

Schematic drawing showing the following five types of membrane proteins: (a) type I transmembrane, (b) type II transmembrane, (c) multipass transmembrane, (d) lipid-chain anchored membrane, and (e) GPI-anchored membrane. As shown from the figure, although both type I and type II membrane proteins are of single-pass transmembrane, type I has a cytoplasmic C-terminus and an extracellular or luminal N-terminus for plasma membrane or organelle membrane, respectively, while the arrangement of N- and C-termini in type II membrane proteins is the reverse. No such distinction was drawn between the extracellular (or luminal) and cytoplasmic sides for the other three types in the current classification scheme. Reproduced from Chou (2001) with permission.