Functional Analysis of Nodulin 26, an Aquaporin in Soybean Root Nodule Symbiosomes

• DOI: 10.1074/jbc.272.26.16256
• Publication Date: 2002-07-26T15:14:15Z
• Authors: Rickey L. Rivers; Robert M. Dean; Grischa Chandy; James E. Hall; Daniel M. Roberts; Mark L. Zeidel
• Keywords: 0301 basic medicine; Aquaporin 1; Glycine max; Xenopus; Membrane Proteins; Water; Biological Transport; Aquaporins; Ion Channels; Permeability; 6. Clean water; 03 medical and health sciences; Oocytes; Animals; Plant Proteins

Upon infection of soybean roots, nitrogen-fixing bacteria become enclosed in a specific organelle known as the symbiosome. The symbiosome membrane (SM) is selectively permeable barrier that controls metabolite flux between plant cytosol and symbiotic bacterium inside. Nodulin 26 (NOD 26), member aquaporin (AQP) water channel family, major protein component SM. Expression NOD Xenopus oocytes gave mercury-sensitive increase osmotic permeability (Pf). To define biophysical properties channels their native membranes, symbiosomes were isolated from root nodules SM separated vesicles bacteria. Permeabilities measured using stopped-flow fluorimetry with entrapped carboxyfluorescein. Osmotic (Pf) was high, value 0.05 +/- 0.003 cm/s observed at 20 degrees C (mean S.E.; n = 15). Water flow exhibited low activation energy, inhibited by HgCl2 (0.1 mM), unit conductance 3.2 1.3 x 10(-15) cm3/s, 30-fold lower than AQP 1, red blood cell channel. Diffusive (Pd) 0.0024 0.0002 cm/s, resulting Pf to Pd ratio 18.3, indicating crosses single file fashion via In addition high permeability, also show glycerol formamide, but not urea, suggesting fluxes these solutes. Overall, we conclude acts 1. Because solutes permeate are far larger water, appears cross pathway, solute across occur pathway distinct for water.