What is the aquaporin water channel?

Aquaporins (AQPs) are water channel proteins that increase cell membrane water permeability and assemble in cell membranes as tetramers.

What is the function of aquaporin channel?

Aquaporins selectively conduct water molecules in and out of the cell, while preventing the passage of ions and other solutes. Also known as water channels, aquaporins are integral membrane pore proteins.

What is the importance of aquaporin membrane channels?

Aquaporins allow water or small specific solutes to pass unhindered, but block the passage of ions to prevent dissipation of the transmembrane potential.

How does water go through aquaporin?

Water crosses cell membranes by two routes: by diffusion through the lipid bilayer and through water channels called aquaporins. The classical aquaporins transport solute-free water across cell membranes; they appear to be exclusive water channels and do not permeate membranes to ions or other small molecules.

How many aquaporin channels are there?

This “first” water channel was originally named CHIP28 and is now known as aquaporin 1. Agre received the Nobel Prize in Chemistry in 2003 for this discovery. There are currently 13 known aquaporins in mammals, distributed in most tissues, but many more have been identified in lower organisms and in the plant kingdom.

How many aquaporins make water channels?

Four aquaporin channels associate with each other in the membrane, so that in one location there are four possible passageways for water to move through the cell membrane. Each aquaporin channel can have a slightly different protein structure.

What is the main aquaporin that is found in the body?

In mammalian cells, more than 10 isoforms (AQP0-AQP10) have been identified so far. They are differentially expressed in many types of cells and tissues in the body. AQP0 is abundant in the lens. AQP1 is found in the blood vessels, kidney proximal tubules, eye, and ear.

Is aquaporin a gated channel?

In eukaryotes aquaporins are frequently gated, either by being directed into various membranes (trafficking) or by regulation of their water-transport activity in the membrane (gating). Plants counteract fluctuations in water supply by regulating all aquaporins in the cell plasma membrane.

Where are aquaporin channels found?

They are differentially expressed in many types of cells and tissues in the body. AQP0 is abundant in the lens. AQP1 is found in the blood vessels, kidney proximal tubules, eye, and ear.

How does oxygen and carbon dioxide pass through the membrane?

Oxygen and carbon dioxide move across cell membranes via simple diffusion, a process that requires no energy input and is driven by differences in concentration on either side of the cell membrane.

Does aquaporin require energy?

To dehydrate an ion, a significant amount of energy would be needed and typically this is counterbalanced by other binding events. In the case of the aquaporin channel, the location where the ions would need to become dehydrated to pass through the pore restriction is associated with hydrophobic amino acid regions.

Is aquaporin active transport?

The primary function of most aquaporins is to transport water across cell membranes in response to osmotic gradients created by active solute transport. A subset of aquaporins, called aquaglyceroporins also transport glycerol.

How does Aquaporin 1 channel protein facilitate water transport?

It is predicted that a single human aquaporin-1 channel protein facilitates water transport at a rate of roughly 3 billion water molecules per second. Such transport appears to be bidirectional, in accordance with the prevailing osmotic gradient.

How did Agre prove that aquaporin is a water channel?

Agre also knew that mercury ions often prevent cells from taking up and releasing water, and he showed that water transport through his artificial membrane sacs with the aquaporin protein was prevented in the same way by mercury. This was further evidence that aquaporin might actually be a water channel.

Where are aquaporins located in the plasma membrane?

Aquaporins (AQPs) constitute a family of proteins with channel functions, which are located in the plasma cell membrane and mediate the water transport [1–3]. A total of 13 proteins (AQP1–12Α, Β) are included in the AQP family in Homo sapiens [1].

What is the role of aquaporin in osmosis?

Aquaporin are intrinsic membrane proteins that serve as water-selective channels, and are involved in compartmentalization of water molecules. They likely play a role in maintaining osmosis and turgor of halophyte cells under salt stress (Dibas et al., 1998).