Uniporter

A uniporter is a membrane transport protein that transports a single species of substrate (charged or uncharged) across a cell membrane. It may use either facilitated diffusion and transport along a diffusion gradient or transport against one with an active transport process.[1] Uniporters include both carriers and ion channels,[2] and are referred to as facilitated transporters, suggesting movement down a concentration or electrochemical gradient.

Comparison of transport proteins

Uniporter carrier proteins work by binding to one molecule of substrate at a time. Uniporter channels open in response to a stimulus and allow the free flow of specific molecules.

There are several ways in which the opening of uniporter channels may be regulated:

  1. Voltage – Regulated by the difference in voltage across the membrane
  2. Stress – Regulated by physical pressure on the transporter (as in the cochlea of the ear)
  3. Ligand – Regulated by the binding of a ligand to either the intracellular or extracellular side of the cell

Uniporters are involved in many biological processes, including action potentials in neurons. Voltage-gated sodium channels are involved in the propagation of a nerve impulse across the neuron. During transmission of the signal from one neuron to the next, calcium is transported into the presynaptic neuron by voltage-gated calcium channels. Potassium leak channels, also regulated by voltage, then help to restore the resting membrane potential after impulse transmission.

In the ear, sound waves cause the stress-regulated channels in the ear to open, sending an impulse to the vestibulocochlear nerve (VIII).

See also

References
  1. Cammack, Richard; Atwood, Teresa; Campbell, Peter; Parish, Howard; Smith, Anthony; Vella, Frank; Stirling, John (2006). "uniport". Oxford Dictionary of Biochemistry and Molecular Biology. Oxford University Press. doi:10.1093/acref/9780198529170.001.0001/acref-9780198529170-e-20301. Retrieved 3 June 2020.
  2. Wolfersberger, MG (November 1994). "Uniporters, Symporters and Antiporters". J Exp Biol. 196: 5–6. PMID 7823043.
  • Alberts, Bruce et al. — Essential Cell Biology, 1st edition. Garland Publishing, New York: 1998.
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