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A membrane transport protein (or simply transporter) is a protein involved in the movement of ions, small molecules, or macromolecules, such as another protein across a biological membrane. Transport proteins are integral membrane proteins; that is they exist within and span the membrane across which they transport substances. The proteins may assist in the movement of substances by facilitated diffusion or active transport.

The mechanism of action of these proteins is known as carrier-mediated transport. There are two forms of carrier-mediated transport, active transport and facilitated diffusion.^[1]

[edit] Facilitated diffusion

Facilitated diffusion

A facilitated diffusion protein speeds the movement of a chemical through a membrane in the absence of energy input; therefore, the transported chemical can move only down a concentration gradient. This can be accomplished by the formation of a high-specificity pore or channel that spans the membrane. These polar "holes" through the membrane are lined by specific amino acids residues that lower the energy barrier to the movement of polar molecules.

[edit] More examples

• Karyopherin
• Mitochondrial membrane transport protein
• Glucose transporter
• ATP-binding cassette transporter genes
  • P-glycoprotein
  • CD98
• CD36
• Neurotransmitter transporters
  • Glutamate transporter
  • Norepinephrine transporter
  • Vesicular monoamine transporter
• V-ATPase
• Ion transporters
  • Na+/K+-ATPase
  • Plasma membrane Ca²⁺ ATPase
  • Proton pump
  • Hydrogen potassium ATPase
  • Sodium-chloride symporter

[edit] See also

• Carrier protein
• Ion channel
• P-loop
• Solute carrier family (classification)
• TC number (classification)
• Vesicular transport protein
• Wikipedia:MeSH_D12.776#MeSH_D12.776.157.530_---_membrane_transport_proteins
• Cotransport
• Cotransporter

[edit] References

[edit] External links

• transport protein at Dorland's Medical Dictionary
• MeSH Membrane+transport+proteins