A uniporter is a
membrane transport protein that transports a single species of
substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (locomotion), the surface over which an organism lo ...
(
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. Uniporters include both carriers and
ion channel
Ion channels are pore-forming membrane proteins that allow ions to pass through the channel pore. Their functions include establishing a resting membrane potential, shaping action potentials and other electrical signals by gating the flow of io ...
s, and are referred to as facilitated transporters, suggesting movement down a concentration or electrochemical gradient.
Uniporter carrier proteins work by binding to one
molecule of
substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (locomotion), the surface over which an organism lo ...
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:
#
Voltage – Regulated by the difference in voltage across the membrane
#
Stress – Regulated by physical
pressure on the transporter (as in the
cochlea of the
ear)
#
Ligand – Regulated by the binding of a ligand to either the intracellular or extracellular side of the
cell
Uniporters are found in mitochondria and neurons. The uniporter in the mitochondria is responsible for calcium uptake. The calcium channels are used for cell signaling and triggering apoptosis. The calcium uniporter transports calcium across the inner mitochondrial membrane and is activated when calcium rises above a certain concentration.
Voltage-gated potassium channel
Voltage-gated potassium channels (VGKCs) are transmembrane channels specific for potassium and sensitive to voltage changes in the cell's membrane potential. During action potentials, they play a crucial role in returning the depolarized ce ...
s are also uniporters that can be found in neurons and are essential for
action potentials. This channel is activated by a voltage gradient created by
sodium-potassium pumps. When the membrane reaches a certain voltage, the channels open which depolarizes the membrane which leads to the action potential being sent down the membrane.
See also
*
Antiporter
An antiporter (also called exchanger or counter-transporter) is a cotransporter and integral membrane protein involved in secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma memb ...
*
Symporter
A symporter is an integral membrane protein that is involved in the transport of two (or more) different molecules across the cell membrane in the same direction. The symporter works in the plasma membrane and molecules are transported across the ...
References
* Alberts, Bruce et al. — ''Essential Cell Biology'', 1st edition. Garland Publishing, New York: 1998.
{{Membrane transport
Integral membrane proteins
Transport phenomena