Aquaporin
Aqvaporin is an integral membrane protein regulating water flow across the membrane.
Function mechanism
Regardless of the temperature, water passes through the pores in membrane integral proteins - porins. These water channels are selective for the passage of water, neither solutes nor small molecules pass through them ( urea has its own specific channel).
Some of these channels are controlled chemically, for others the regulation is not yet known.
High specificity is achieved with a channel diameter of 0.2 nm (not even H+, OH- does not pass through). Water passes through a continuous stream of 2-4.109 molecules per second.
Structure
- Molecular weight 30 kDa;
- 6 hydrophobic sections (domains);
- molecules form tetramers (water passes through each molecule separately);
- 10 types of aquaporin H (AQP0–AQP9);
Occurrence
| Localization | A type of aqvaporin |
|---|---|
| Erythrocytes | AQP1 |
| Distal segment of nephron | AQP2,3 |
| Plexus choroideus | APQ1 |
| Lung | APQ4 |
| Salivary and lacrimal glands | APQ5 |
Their permeability is in many cases controlled by vasopressin (AQP2).
Links
External links
References
- LANGMEIER, Miloš. Základy lékařské fyziologie. 1. edition. Praha : Grada Publishing, a.s, 2009. 320 pp. ISBN 978-80-247-2526-0.
