A membrane transport protein (or simply transporter) is a membrane protein

Membrane protein

A membrane protein is a protein molecule that is attached to, or associated with the membrane of a cell or an organelle. More than half of all proteins interact with membranes.-Function:...

 involved in the movement of ion

Ion

An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...

s, small molecule

Molecule

A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...

s, or macromolecule

Macromolecule

A macromolecule is a very large molecule commonly created by some form of polymerization. In biochemistry, the term is applied to the four conventional biopolymers , as well as non-polymeric molecules with large molecular mass such as macrocycles...

s, such as another protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 across a biological membrane

Biological membrane

A biological membrane or biomembrane is an enclosing or separatingmembrane that acts as a selective barrier, within or around a cell. It consists of a lipid bilayer with embedded proteins that may constitute close to 50% of membrane content...

. Transport proteins are integral membrane protein

Integral membrane protein

An integral membrane protein is a protein molecule that is permanently attached to the biological membrane. Proteins that cross the membrane are surrounded by "annular" lipids, which are defined as lipids that are in direct contact with a membrane protein...

s; 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

Active transport

Active transport is the movement of a substance against its concentration gradient . In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose, and amino acids. If the process uses chemical energy, such as from adenosine...

. These mechanisms of action are known as carrier-mediated transport.

Types

(Grouped by Transporter Classification database categories)

2: Electrochemical Potential-driven transporters

• Mitochondrial membrane transport protein
  Mitochondrial membrane transport protein
  Mitochondrial membrane transport proteins are proteins which exist in the membranes of mitochondria and which serve to transport molecules and other factors such as ions into or out of the organelles.-Examples:...
  
  
• Glucose transporter
  Glucose transporter
  Glucose transporters are a wide group of membrane proteins that facilitate the transport of glucose over a plasma membrane. Because glucose is a vital source of energy for all life these transporters are present in all phyla...
  
  
• Neurotransmitter transporter
  Neurotransmitter transporter
  Neurotransmitter transporters are a class of membrane transport proteins that span the cellular membranes of neurons. Their primary function is to carry neurotransmitters across these membranes and to direct their further transport to specific intracellular locations...
  
  s
  • Glutamate/aspartate transporter
    Glutamate transporter
    Excitatory amino-acid transporters , formerly known as Glutamate transporters, belong to the family of neurotransmitter transporters. They serve to terminate the excitatory neurotransmitter signal by removal of glutamate from the neuronal synapse into Glia cells.In details, the EAATs are...
    
    s
  • GABA transporter
    GABA transporter
    GABA transporters are Neurotransmitter transporters including:** GABA transporter type 1 ** GABA transporter type 2 ** GABA transporter type 3 ** Betaine transporter ** Vesicular GABA transporter...
    
    s
  • Glycine transporters
  • Monoamine transporter
    Monoamine transporter
    Monoamine transporters are protein structures that function as integral plasma membrane transporters to regulate concentrations of extracellular monoamine neurotransmitters. Three major classes of MATs are responsible for the reuptake of their associated amine neurotransmitters...
    
    s, including:
    • Dopamine transporter
      Dopamine transporter
      The dopamine transporter is a membrane-spanning protein that pumps the neurotransmitter dopamine out of the synapse back into cytosol, from which other transporters sequester DA and NE into vesicles for later storage and release...
      
       (DAT)
    • Norepinephrine transporter
      Norepinephrine transporter
      The norepinephrine transporter , also known as solute carrier family 6 member 2 , is a protein that in humans is encoded by the SLC6A2 gene....
      
       (NET)
    • Serotonin transporter
      Serotonin transporter
      The serotonin transporter is a monoamine transporter protein.This protein is an integral membrane protein that transports the neurotransmitter serotonin from synaptic spaces into presynaptic neurons. This transport of serotonin by the SERT protein terminates the action of serotonin and recycles it...
      
       (SERT)
    • Vesicular monoamine transporter
      Vesicular monoamine transporter
      The vesicular monoamine transporter is a transport protein integrated into the membrane of intracellular vesicles of presynaptic neurons. It acts to transport monoamines into the synaptic vesicles.-Monoamines:...
      
      s (VMAT)
  • Adenosine transporter
    Equilibrative nucleoside transporter
    The equilibrative nucleoside transporter family, also known as SLC29, is a group of plasmalemmal transport proteins which transport nucleoside substrates like adenosine into cells. There are four known ENTs, designated ENT1, ENT2, ENT3, and ENT4...
    
    s
  • Vesicular acetylcholine transporter
    Vesicular acetylcholine transporter
    The Vesicular acetylcholine transporter is a neurotransmitter transporter which is responsible for loading acetylcholine into secretory organelles in neurons making acetylcholine available for secretion.-Radiolabeled compounds:...
    
     (VAChT)

3: Primary Active Transporters

• ATP-binding cassette transporter genes
  ATP-binding cassette transporter genes
  ATP-binding cassette transporters are members of a protein superfamily that is one of the largest and most ancient families with representatives in all extant phyla from prokaryotes to humans...
  
  
  • P-glycoprotein
    P-glycoprotein
    P-glycoprotein 1 also known as multidrug resistance protein 1 or ATP-binding cassette sub-family B member 1 or cluster of differentiation 243 is a glycoprotein that in humans is encoded by the ABCB1 gene...
    
    
  • CD98
    CD98
    CD98 is a glycoprotein that is a heterodimer composed of SLC3A2 and SLC7A5 that forms the large neutral amino acid transporter . LAT1 is a heterodimeric membrane transport protein that preferentially transports branched-chain and aromatic amino acids...
    
    
• V-ATPase
  V-ATPase
  Vacuolar-type H+-ATPase is a highly conserved evolutionarily ancient enzyme with remarkably diverse functions in eukaryotic organisms. V-ATPases acidify a wide array of intracellular organelles and pump protons across the plasma membranes of numerous cell types...
  
  
• Ion transporters
  • Na+/K+-ATPase
    Na+/K+-ATPase
    Na+/K+-ATPase is an enzyme located in the plasma membrane in all animals.- Sodium-potassium pumps :Active transport is responsible for cells containing relatively high...
    
    
  • Plasma membrane Ca²⁺ ATPase
  • Proton pump
    Proton pump
    A proton pump is an integral membrane protein that is capable of moving protons across a cell membrane, mitochondrion, or other organelle. Mechanisms are based on conformational changes of the protein structure or on the Q cycle.-Function:...
    
    
  • Hydrogen potassium ATPase
    Hydrogen potassium ATPase
    Gastric hydrogen potassium ATPase is also known as H+/K+ ATPase- Function and location :The gastric hydrogen potassium ATPase or H+/K+ ATPase is the proton pump of the stomach and, as such, is the enzyme primarily responsible for the acidification of the stomach contents...
    
    
  • Sodium-chloride symporter
    Sodium-chloride symporter
    The sodium-chloride symporter is a cotransporter in the kidney which has the function of reabsorbing sodium and chloride ions from the tubular fluid into the cells of the distal convoluted tubule of the nephron.It is a member of the SLC12...
    
    

4: Co-transporters

Symporters transport two or more ions together in the same direction, antiporter

Antiporter

An antiporter is an integral membrane protein involved in secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions.In secondary active transport, one species of solute moves along its electrochemical...

s in the opposite direction.

See also

• Carrier protein
  Carrier protein
  Carrier proteins are proteins involved in the movement of ions, small molecules, or macromolecules, such as another protein, across a biological membrane. Carrier proteins are integral membrane proteins; that is they exist within and span the membrane across which they transport substances. The...
  
  
• Cotransport
  Co-transport
  Co-transport, also known as coupled transport or secondary active transport, refers to the simultaneous or sequential passive transfer of molecules or ions across biological membranes in a fixed ratio...
  
  
• Cotransporter
• Ion channel
  Ion channel
  Ion channels are pore-forming proteins that help establish and control the small voltage gradient across the plasma membrane of cells by allowing the flow of ions down their electrochemical gradient. They are present in the membranes that surround all biological cells...
  
  
• P-loop
• Solute carrier family
  Solute carrier family
  The solute carrier group of membrane transport proteins include over 300 members organized into 51 families. The SLC gene nomenclature system was originally proposed by the Human Genome Organization and is the basis for the official HUGO names of the genes that encode these transporters...
  
   (classification)
• TC number
  TC number
  Transporter Classification database is an International Union of Biochemistry and Molecular Biology approved classification system for membrane transport proteins including ion channels...
  
   (classification)
• Vesicular transport protein
  Vesicular transport protein
  A vesicular transport protein is a transmembrane or membrane associated protein. It regulates or facilitates the movement by vesicles of the contents of the cell.-Types:Examples include:* Archain* ARFs* Clathrin* Caveolin...
  
  

External links