scholarly journals Single-file transport of water through membrane channels

2018 ◽  
Vol 209 ◽  
pp. 9-33 ◽  
Author(s):  
Andreas Horner ◽  
Peter Pohl
Keyword(s):  
Potassium Channels ◽  
Water Permeability ◽  
Transport Theory ◽  
Water Channel ◽  
Gramicidin A ◽  
Membrane Channels ◽  
Short Introduction ◽  
Channel Proteins ◽  
Single File ◽  
Single File Transport

After a short introduction into the single-file transport theory, we analyze experiments in which the unitary water permeability, pf, of water channel proteins (aquaporins, AQPs), potassium channels (KcsA), and antibiotics (gramicidin-A derivatives) has been obtained. A short outline of the underlying methods is also provided.

scholarly journals Water permeability of gramicidin A-treated lipid bilayer membranes.

1978 ◽  
Vol 72 (3) ◽  
pp. 341-350 ◽  
Author(s):  
P A Rosenberg ◽  
A Finkelstein
Keyword(s):  
Water Permeability ◽  
Permeability Coefficient ◽  
Pore Radius ◽  
Gramicidin A ◽  
Water Molecules ◽  
Lipid Bilayer Membranes ◽  
Bilayer Membranes ◽  
Single File ◽  
Water Permeability Coefficient ◽  
Single File Transport

In membranes containing aqueous pores (channels), the osmotic water permeability coefficient, P f, is greater than the diffusive water permeability coefficient, P d. In fact, the magnitude of P f/P d is commonly used to determine pore radius. Although, for membranes studied to date, P f/P d monotonically declines with decreasing pore radius, there is controversy over the value it theoretically assumes when that radius is so small that water molecules cannot overtake one another within the channel (single-file transport). In one view it should equal 1, and in another view it should equal N, the number of water molecules in the pore. Gramicidin A forms, in lipid bilayer membranes, narrow aqueous channels through which single-file transport may occur. For these channels we find that P f/P d approximately 5. In contrast, for the wider nystatin and amphotericin B pores, P f/P d approximately 3. These findings offer experimental support for the view that P f/P d = N for single-file transport, and we therefore conclude that there are approximately five water molecules in a gramicidin A channel. A similar conclusion was reached independently from streaming potential data. Using single-channel conductance data, we calculate the water permeability of an individual gramicidin A channel. In the Appendix we report that there is a wide range of channel sizes and lifetimes in cholesterol-containing membranes.

scholarly journals Water Dynamics in a Peptide-appended Pillar[5]arene Artificial Channel in Lipid and Biomimetic Membranes

2021 ◽  
Vol 9 ◽  
Author(s):  
Daniel Ryan Barden ◽  
Harish Vashisth
Keyword(s):  
Free Energy ◽  
Water Channel ◽  
Md Simulations ◽  
High Water ◽  
Chem Phys ◽  
Water Dynamics ◽  
Free Energy Surface ◽  
Biological Water ◽  
Single File ◽  
Single File Transport

Peptide-appended Pillar[5]arene (PAP) is an artificial water channel that can be incorporated into lipid and polymeric membranes to achieve high permeability and enhanced selectivity for angstrom-scale separations [Shen et al. Nat. Commun.9:2294 (2018)]. In comparison to commonly studied rigid carbon nanotubes, PAP channels are conformationally flexible, yet these channels allow a high water permeability [Y. Liu and H. Vashisth Phys. Chem. Chem. Phys.21:22711 (2019)]. Using molecular dynamics (MD) simulations, we study water dynamics in PAP channels embedded in biological (lipid) and biomimetic (block-copolymer) membranes to probe the effect of the membrane environment on water transport characteristics of PAP channels. We have resolved the free energy surface and local minima for water diffusion within the channel in each type of membrane. We find that water follows single file transport with low free-energy barriers in regions surroundings the central ring of the PAP channel and the single file diffusivity of water correlates with the number of hydrogen bonding sites within the channel, as is known for other sub-nm pore-size synthetic and biological water channels [Horner et al. Sci. Adv.1:e1400083 (2015)].

Cellular mechanisms of aquaporin trafficking

1998 ◽  
Vol 275 (3) ◽  
pp. F328-F331 ◽  
Author(s):  
Dennis Brown ◽  
Toshiya Katsura ◽  
Corinne E. Gustafson
Keyword(s):  
Recent Work ◽  
Water Channel ◽  
Short Review ◽  
Cellular Mechanisms ◽  
Channel Proteins ◽  
Intracellular Targeting ◽  
Biological Interest

Aquaporins (AQPs) are a family of functionally important water channel proteins that are of special cell biological interest because of their diverse intracellular targeting and trafficking properties. AQPs have been found in many different cells and tissues. This short review summarizes recent work that addresses the regulation of AQP2 trafficking in response to vasopressin.

The aquaporins. A family of water channel proteins

1998 ◽  
Vol 30 (2) ◽  
pp. 169-172 ◽  
Author(s):  
D.L Connolly ◽  
C.M Shanahan ◽  
P.L Weissberg
Keyword(s):  
Water Channel ◽  
Channel Proteins

Progesterone inhibition of water permeability in Bufo arenarum oocytes and urinary bladder

1996 ◽  
Vol 270 (5) ◽  
pp. F880-F885 ◽  
Author(s):  
P. Ford ◽  
G. Amodeo ◽  
C. Capurro ◽  
C. Ibarra ◽  
R. Dorr ◽  
...  
Keyword(s):  
Urinary Bladder ◽  
Xenopus Laevis ◽  
Water Permeability ◽  
Water Channel ◽  
Water Channels ◽  
Toad Urinary Bladder ◽  
Osmotic Permeability ◽  
Bufo Arenarum ◽  
Mrna Extraction

The ovarian oocytes from Bufo arenarum (BAO) but not those from Xenopus laevis (XLO) would have water channels (WC). We now report that the injection of the mRNA from BAO into the oocytes from XLO increased their water osmotic permeability (Pi) (reduced by 0.3 mM HgCl2 and reversed by 5 mM beta-mercaptoethanol). A 30-min challenge with progesterone induced, 18 h later, a reduction of the mercury-sensitive fraction of Pf in the BAO (but not in XLO). The mRNA from BAO pretreated with progesterone lost its capacity to induce WC in the XLO, but the hormone did not affect the expression of the WC in XLO previously injected with the mRNA from BAO. Pf was also measured in urinary bladders of BAO. Eighteen hours after a challenge with progesterone, a reduction in the hydrosmotic response to oxytocin was observed. Finally, the mRNA from the urinary bladder of BAO was injected into XLO. An increase in Pf was observed. This was not the case if, before the mRNA extraction, the bladders were treated with progesterone. We conclude that the BAO WC share progesterone sensitivity with the oxytocin-regulated water channel present in the toad urinary bladder.

Cloning and functional expression of an MIP (AQP0) homolog from killifish (Fundulus heteroclitus) lens

2001 ◽  
Vol 281 (6) ◽  
pp. R1994-R2003 ◽  
Author(s):  
Leila V. Virkki ◽  
Gordon J. Cooper ◽  
Walter F. Boron
Keyword(s):  
Water Permeability ◽  
Fundulus Heteroclitus ◽  
Water Channel ◽  
Fold Increase ◽  
Functional Expression ◽  
Xenopus Laevis Oocytes ◽  
Lens Fiber ◽  
Fiber Cells ◽  
Aqp1 Expression ◽  
Very High

The major intrinsic protein (MIP) of lens fiber cells is a member of the aquaporin (AQP) water channel family. The protein is expressed at very high levels in lens fiber cells, but its physiological function is unclear. By homology to known AQPs, we have cloned a full-length cDNA encoding an MIP from the lens of killifish ( Fundulus heteroclitus). The predicted protein (263 amino acids; GenBank accession no. AF191906 ) shows 77% identity to amphibian MIPs, 70% identity to mammalian MIPs, and 46% identity to mammalian AQP1. Expression of MIPfun in Xenopus laevis oocytes causes an ∼40-fold increase in oocyte water permeability. This stimulation is comparable to that seen with AQP1 and substantially larger than that seen with other MIPs. The mercurials HgCl2 and p-chloromercuribenzenesulfonate inhibit the water permeability of MIPfun by ∼25%. MIPfun is not permeable to glycerol, urea, or formic acid but is weakly permeable to CO2.

Conformational dynamics and interfacial interactions of peptide-appended pillar[5]arene water channels in biomimetic membranes

2019 ◽  
Vol 21 (41) ◽  
pp. 22711-22721 ◽  
Author(s):  
Yong Liu ◽  
Harish Vashisth
Keyword(s):  
Water Purification ◽  
Conformational Dynamics ◽  
Water Channel ◽  
Water Channels ◽  
Interfacial Interactions ◽  
Biomimetic Membranes ◽  
Channel Proteins ◽  
Significant Potential ◽  
Biological Water ◽  
Artificial Water

Peptide appended pillar[5]arene (PAP) is an artificial water channel resembling biological water channel proteins, which has shown a significant potential for designing bioinspired water purification systems.

scholarly journals The Vasopressin Receptor 2 Mutant R137L Linked to the Nephrogenic Syndrome of Inappropriate Antidiuresis (NSIAD) Signals through an Alternative Pathway that Increases AQP2 Membrane Targeting Independently of S256 Phosphorylation

Cells ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1354
Author(s):  
Marianna Ranieri ◽  
Maria Venneri ◽  
Tommaso Pellegrino ◽  
Mariangela Centrone ◽  
Annarita Di Mise ◽  
...  
Keyword(s):  
Water Permeability ◽  
Collecting Duct ◽  
Alternative Pathway ◽  
Water Channel ◽  
Rho Kinase ◽  
Membrane Targeting ◽  
Rock Inhibitor ◽  
Activating Mutations ◽  
Osmotic Water

NSIAD is a rare X-linked condition, caused by activating mutations in the AVPR2 gene coding for the vasopressin V2 receptor (V2R) associated with hyponatremia, despite undetectable plasma vasopressin levels. We have recently provided in vitro evidence that, compared to V2R-wt, expression of activating V2R mutations R137L, R137C and F229V cause a constitutive redistribution of the AQP2 water channel to the plasma membrane, higher basal water permeability and significantly higher basal levels of p256-AQP2 in the F229V mutant but not in R137L or R137C. In this study, V2R mutations were expressed in collecting duct principal cells and the associated signalling was dissected. V2R-R137L and R137C mutants had significantly higher basal pT269-AQP2 levels -independently of S256 and PKA-which were reduced to control by treatment with Rho kinase (ROCK) inhibitor. Interestingly, ROCK activity was found significantly higher in V2R-R137L along with activation of the Gα12/13–Rho–ROCK pathway. Of note, inhibition of ROCK reduced the basal elevated osmotic water permeability to control. To conclude, our data demonstrate for the first time that the gain-of-function mutation of the V2R, R137L causing NSIAD, signals through an alternative PKA-independent pathway that increases AQP2 membrane targeting through ROCK-induced phosphorylation at S/T269 independently of S256 of AQP2.

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