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Structural characterization of two aquaporins isolated from native spinach leaf plasma membranes

Fotiadis, D. and Jeno, P. and Mini, T. and Wirtz, S. and Muller, S. A. and Fraysse, L. and Kjellbom, P. and Engel, A.. (2001) Structural characterization of two aquaporins isolated from native spinach leaf plasma membranes. Journal of Biological Chemistry, Vol. 276, H. 3. pp. 1707-1714.

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Official URL: http://edoc.unibas.ch/dok/A5257659

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Abstract

Two members of the aquaporin family, PM28A and a new one, PM28C, were isolated and shown to be the major constituents of spinach leaf plasma membranes. These two isoforms were identified and characterized by matrix-assisted laser desorption ionization-mass spectrometry. Edman degradation yielded the amino acid sequence of two domains belonging to the new isoform. PM28B, a previously described isoform, was not found in our preparations. Scanning transmission electron microscopy mass analysis revealed both PM28 isoforms to be tetrameric. Two types of particles, a larger and a smaller one, were found by transmission electron microscopy of negatively stained solubilized proteins and by atomic force microscopy of PM28 two-dimensional crystals. The ratio of larger to smaller particles observed by transmission electron microscopy and single particle analysis correlated with the ratio of PM28A to PM28C determined by matrix-assisted laser desorption ionization-mass spectrometry. The absence of PM28B and the ratio of PM28A to PM28C indicate that these plasma membrane intrinsic proteins are differentially expressed in spinach leaves. These findings suggest that differential expression of the various aquaporin isoforms may regulate the water flux across the plasma membrane, in addition to the known mechanism of regulation by phosphorylation.
Faculties and Departments:05 Faculty of Science > Departement Biozentrum > Former Organization Units Biozentrum > Structural Biology (Engel)
05 Faculty of Science > Departement Biozentrum > Services Biozentrum > Mass Spectrometry (Jenö)
UniBasel Contributors:Engel, Andreas H and Jenö, Paul
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:American Society of Biological Chemists
ISSN:0021-9258
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:14 Sep 2012 06:48
Deposited On:22 Mar 2012 13:18

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