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Functional reconstitution and characterization of AqpZ, the E. coli water channel protein.

Publication ,  Journal Article
Borgnia, MJ; Kozono, D; Calamita, G; Maloney, PC; Agre, P
Published in: J Mol Biol
September 3, 1999

Understanding the selectivity of aquaporin water channels will require structural and functional studies of wild-type and modified proteins; however, expression systems have not previously yielded aquaporins in the necessary milligram quantities. Here we report expression of a histidine-tagged form of Escherichia coli aquaporin-Z (AqpZ) in its homologous expression system. 10-His-AqpZ is solubilized and purified to near homogeneity in a single step with a final yield of approximately 2.5 mg/l of culture. The histidine tag is removed by trypsin, yielding the native protein with the addition of three N-terminal residues, as confirmed by microsequencing. Sucrose gradient sedimentation analysis showed that the native, solubilized AqpZ protein is a trypsin-resistant tetramer. Unlike other known aquaporins, AqpZ tetramers are not readily dissociated by 1% SDS at neutral pH. Hydrophilic reducing agents have a limited effect on the stability of the tetramer in 1% SDS, whereas incubations for more than 24 hours, pH values below 5.6, or exposure to the hydrophobic reducing agent ethanedithiol cause dissociation into monomers. Cys20, but not Cys9, is necessary for the stability of the AqpZ tetramer in SDS. Upon reconstitution into proteoliposomes, AqpZ displays very high osmotic water permeability (pf > or = 10 x 10(-14) cm3 s-1 subunit-1) and low Arrhenius activation energy (Ea = 3.7 kcal/mol), similar to mammalian aquaporin-1 (AQP1). No permeation by glycerol, urea or sorbitol was detected. Expression of native and modified AqpZ in milligram quantities has permitted biophysical characterization of this remarkably stable aquaporin tetramer, which is being utilized for high-resolution structural studies.

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Published In

J Mol Biol

DOI

ISSN

0022-2836

Publication Date

September 3, 1999

Volume

291

Issue

5

Start / End Page

1169 / 1179

Location

Netherlands

Related Subject Headings

  • Water
  • Trypsin
  • Structure-Activity Relationship
  • Solubility
  • Sodium Dodecyl Sulfate
  • Reducing Agents
  • Recombinant Fusion Proteins
  • Proteolipids
  • Protein Conformation
  • Permeability
 

Citation

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Borgnia, M. J., Kozono, D., Calamita, G., Maloney, P. C., & Agre, P. (1999). Functional reconstitution and characterization of AqpZ, the E. coli water channel protein. J Mol Biol, 291(5), 1169–1179. https://doi.org/10.1006/jmbi.1999.3032
Borgnia, M. J., D. Kozono, G. Calamita, P. C. Maloney, and P. Agre. “Functional reconstitution and characterization of AqpZ, the E. coli water channel protein.J Mol Biol 291, no. 5 (September 3, 1999): 1169–79. https://doi.org/10.1006/jmbi.1999.3032.
Borgnia MJ, Kozono D, Calamita G, Maloney PC, Agre P. Functional reconstitution and characterization of AqpZ, the E. coli water channel protein. J Mol Biol. 1999 Sep 3;291(5):1169–79.
Borgnia, M. J., et al. “Functional reconstitution and characterization of AqpZ, the E. coli water channel protein.J Mol Biol, vol. 291, no. 5, Sept. 1999, pp. 1169–79. Pubmed, doi:10.1006/jmbi.1999.3032.
Borgnia MJ, Kozono D, Calamita G, Maloney PC, Agre P. Functional reconstitution and characterization of AqpZ, the E. coli water channel protein. J Mol Biol. 1999 Sep 3;291(5):1169–1179.
Journal cover image

Published In

J Mol Biol

DOI

ISSN

0022-2836

Publication Date

September 3, 1999

Volume

291

Issue

5

Start / End Page

1169 / 1179

Location

Netherlands

Related Subject Headings

  • Water
  • Trypsin
  • Structure-Activity Relationship
  • Solubility
  • Sodium Dodecyl Sulfate
  • Reducing Agents
  • Recombinant Fusion Proteins
  • Proteolipids
  • Protein Conformation
  • Permeability