Boron bridging of rhamnogalacturonan-II is promoted in vitro by cationic chaperones, including polyhistidine and wall glycoproteins
© 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.
| Veröffentlicht in: | The New phytologist. - 1979. - 209(2016), 1 vom: 15. Jan., Seite 241-51 |
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| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2016
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| Zugriff auf das übergeordnete Werk: | The New phytologist |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Boron cell wall cross-linking dehydroascorbic acid extension pectic polysaccharides polyhistidine rhamnogalacturonan-II (RG-II) mehr... |
| Zusammenfassung: | © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust. Dimerization of rhamnogalacturonan-II (RG-II) via boron cross-links contributes to the assembly and biophysical properties of the cell wall. Pure RG-II is efficiently dimerized by boric acid (B(OH)3 ) in vitro only if nonbiological agents for example Pb(2+) are added. By contrast, newly synthesized RG-II domains dimerize very rapidly in vivo. We investigated biological agents that might enable this. We tested for three such agents: novel enzymes, borate-transferring ligands and cationic 'chaperones' that facilitate the close approach of two polyanionic RG-II molecules. Dimerization was monitored electrophoretically. Parsley shoot cell-wall enzymes did not affect RG-II dimerization in vitro. Borate-binding ligands (apiose, dehydroascorbic acid, alditols) and small organic cations (including polyamines) also lacked consistent effects. Polylysine bound permanently to RG-II, precluding electrophoretic analysis. However, another polycation, polyhistidine, strongly promoted RG-II dimerization by B(OH)3 without irreversible polyhistidine-RG-II complexation. Likewise, partially purified spinach extensins (histidine/lysine-rich cationic glycoproteins), strongly promoted RG-II dimerization by B(OH)3 in vitro. Thus certain polycations, including polyhistidine and wall glycoproteins, can chaperone RG-II, manoeuvring this polyanionic polysaccharide domain such that boron-bridging is favoured. These chaperones dissociate from RG-II after facilitating its dimerization, indicating that they act catalytically rather than stoichiometrically. We propose a natural role for extensin-RG-II interaction in steering cell-wall assembly |
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| Beschreibung: | Date Completed 27.09.2016 Date Revised 30.09.2020 published: Print-Electronic Citation Status MEDLINE |
| ISSN: | 1469-8137 |
| DOI: | 10.1111/nph.13596 |