The Plasma Membrane of Arabidopsis thaliana Contains a Mercury-Insensitive Aquaporin That Is a Homolog of the Tonoplast Water Channel Protein TIP
- 1 December 1994
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 106 (4), 1325-1333
- https://doi.org/10.1104/pp.106.4.1325
Abstract
Plant cells contain proteins that are members of the major intrinsic protein (MIP) family, an ancient family of membrane channel proteins characterized by six membrane-spanning domains and two asparagine-proline-alanine (NPA) amino acid motifs in the two halves of the protein. We recently demonstrated that [gamma]-TIP, one of the MIP homologs found in the vacuolar membrane of plant cells, is an aquaporin or water channel protein (C. Maurel, J. Reizer, J.I. Schroeder, M.J. Chrispeels [1993] EMBO J 12: 2241–2247). RD28, another MIP homolog in Arabidopsis thaliana, was first identified as being encoded by a turgor-responsive transcript. To find out if RD28 is a water channel protein, rd28 cRNA was injected into Xenopus laevis oocytes. Expression of RD28 caused a 10- to 15-fold increase in the osmotic water permeability of the oocytes, indicating that the protein creates water channels in the plasma membrane of the oocytes and is an aquaporin just like its homolog [gamma]-TIP. Although RD28 has several cysteine residues, its activity is not inhibited by mercury, and in this respect it differs from [gamma]-TIP and all but one of the mammalian water channels that have been described. Introduction of a cysteine residue next to the second conserved NPA motif creates a mercury-sensitive water channel, suggesting that this conserved loop is critical to the activity of the protein. Antibodies directed at the C terminus of RD28 were used in combination with a two-phase partitioning method to demonstrate that RD28 is located in the plasma membrane. The protein is present in leaves and roots of well-watered plants, suggesting that its presence in plants does not require a specific desiccation regime. These results demonstrate that plant cells contain constitutively expressed aquaporins in their plasma membranes (RD28), as well as in their tonoplasts ([gamma]-TIP).Keywords
This publication has 21 references indexed in Scilit:
- Functional characterization of the Escherichia coli glycerol facilitator, GlpF, in Xenopus oocytes.Journal of Biological Chemistry, 1994
- Tetrameric assembly of CHIP28 water channels in liposomes and cell membranes: a freeze-fracture study.The Journal of cell biology, 1993
- The mercury-sensitive residue at cysteine 189 in the CHIP28 water channel.Journal of Biological Chemistry, 1993
- Reconstitution of functional water channels in liposomes containing purified red cell CHIP28 proteinBiochemistry, 1992
- Appearance of Water Channels in Xenopus Oocytes Expressing Red Cell CHIP28 ProteinScience, 1992
- Characterization of cis-acting sequences regulating root-specific gene expression in tobacco.Plant Cell, 1991
- An intrinsic tonoplast protein of protein storage vacuoles in seeds is structurally related to a bacterial solute transporter (GIpF).Plant Cell, 1990
- In vitro mutated phytohemagglutinin genes expressed in tobacco seeds: role of glycans in protein targeting and stability.Plant Cell, 1989
- A complete, yet flexible, system for DNA/protein sequence analysis using VAX/VMS computersBioinformatics, 1988
- Biochemical Effects of Mercury, Cadmium, and LeadAnnual Review of Biochemistry, 1972