Skip to main page content
U.S. flag
See More

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2006 Aug 1;91(3):842-8.
doi: 10.1529/biophysj.106.081406. Epub 2006 May 12.

Does CO2 permeate through aquaporin-1?

Jochen S Hub  1 , Bert L de Groot
Affiliations

Does CO2 permeate through aquaporin-1?

Jochen S Hub et al. Biophys J. .

Abstract

Aquaporins facilitate water permeation across biological membranes. Additionally, glycerol and other small neutral solutes are permeated by related aquaglyceroporins. The role of aquaporins in gas permeation has been a long-standing and controversially discussed issue. We present an extensive set of atomistic molecular dynamics simulations that address the question of CO(2) permeation through human aquaporin-1. Free energy profiles derived from the simulations display a barrier of approximately 23 kJ/mol in the aromatic/arginine constriction region of the water pore, whereas a barrier of approximately 4 kJ/mol was observed for a palmitoyloleoylphosphatidylethanolamine lipid bilayer membrane. The results indicate that significant aquaporin-1-mediated CO(2) permeation is to be expected only in membranes with a low intrinsic CO(2) permeability.

PubMed Disclaimer

Figures

FIGURE 1
FIGURE 1
(a) Typical simulation setup of an AQP1 tetramer, solvated in a POPE bilayer and water. Five CO2 molecules in bulk water are shown in blue and red. (b) In the top view, the four monomeric water pores and the central cavity can be identified. (c) A snapshot taken from an equilibrium simulation showing a water pore (helices and ribbon representation) filled by a single file of water, and the central cavity along the fourfold axis of the tetramer (surface representation). The surface representation is colored according to residue hydrophobicity: hydrophobic residues in orange, hydrophilic residues in blue. All figures with molecular representations were made with PyMOL (50).
FIGURE 2
FIGURE 2
Free energy profile for CO2 permeation through the aquaporin-1 water pore (black, solid line), the tetrameric central cavity (black, dashed line), and a POPE bilayer (shaded).
FIGURE 3
FIGURE 3
Trajectories of unrestrained CO2 molecules in the monomeric AQP1 channel (a), and profiles of enthalpic interactions of CO2 with water (green), protein or POPE, respectively (blue), and total (red) together with the free energy profiles of (cf. Fig. 2, black) for the monomeric channel (b), the central channel around the tetramer axis (c), and through the POPE bilayer (d). The enthalpic profiles only show interactions involving CO2 and do not contain interactions within the CO2's surroundings.
FIGURE 4
FIGURE 4
Free energy profiles of water through the monomeric AQP1 pore obtained by umbrella simulations (solid) and from evaluation of the water density distribution (shaded).
FIGURE 5
FIGURE 5
A CO2 at various positions along the water channel indicating a possible pathway for CO2 along the NPA motifs and through the aromatic/arginine constriction region. The CO2 molecule is colored in red and marine blue. On top of the sequence, the corresponding free energy is plotted, indicating the 23 kJ/mol barrier putatively caused by competition for hydrogen bonds with Arg-195. Note that frequent hydrogen bonds between water molecules and Arg-195 break upon CO2 passage.
See this image and copyright information in PMC

References

    1. Preston, G. M., T. P. Carroll, W. B. Guggino, and P. Agre. 1992. Appearance of water channels in Xenopus oocytes expressing red-cell CHIP28 protein. Science. 256:385–387. - PubMed
    1. Zeidel, M. L., S. V. Ambudkar, B. L. Smith, and P. Agre. 1992. Reconstitution of functional water channels in liposomes containing purified red-cell CHIP28 protein. Biochemistry. 31:7436–7440. - PubMed
    1. Maurel, C., J. Reizer, J. I. Schroeder, M. J. Chrispeels, and M. H. Saier. 1994. Functional characterization of the Eschericia coli glycerol facilitator, GlpF, in Xenopus oocytes. J. Biol. Chem. 269:11869–11872. - PubMed
    1. Agre, P., M. Bonhivers, and M. J. Borgnia. 1998. The aquaporins, blueprints for cellular plumbing systems. J. Biol. Chem. 273:14659–14662. - PubMed
    1. Deen, P. M. T., and C. H. van Os. 1998. Epithelial aquaporins. Curr. Opin. Cell Biol. 10:435–442. - PubMed

Publication types

LinkOut - more resources