4 TYPES OF TRANSMEMBRANE PROTEINS

• Type I membrane proteins have a signal sequence at their N-terminus and an internal stop-transfer sequence. They have no cytosolic tail because signal peptidase cleaves it.

• Type II have an internal signal. Their C term is luminal, and their N term is cytosolic.

• Type III have an internal signal sequence. Their C term is cytosolic, and their N term is luminal.

• Type IV are multipass membrane proteins that have multiple internal stop transfer sequences and start transfer sequences.