Membrane Protein Function Overview

Membrane Proteins

• Found on the surface, embedded, or spanning the lipid bi-layer of the membrane
• Hydrophobic residues are found on the portions interacting with the lipid bi-layer
• Classified by function

Transporters

• Move substrates from a high concentration to a low concentration across the plasma membrane (substrate gradient)
• Transporters have very specific binding sites that are used to recognize their corresponding substrate
• They transition from an open phase to a closed phase during transport

Pumps/Active transport

• Moves substrates against their concentration gradient
• Requires external energy (ATP)
• Result in a conformational change of the protein

Receptor Proteins

• Nothing is transported across the plasma membrane, rather the ligand binding to the receptor on the outside of the membrane results in a signal to be generated on the internal side of the membrane
• Receptor proteins can span the membrane once or multiple times
• Many classes of receptors exist based on structure and method of signal transmission