An Arabidopsis thaliana arabinogalactan-protein (AGP31) and several cationic AGP fragments catalyse the boron bridging of rhamnogalacturonan-II
| Autor: | Dayan Sanhueza, Rifat Ara Begum, Cécile Albenne, Elisabeth Jamet, Stephen C. Fry |
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| Rok vydání: | 2022 |
| Předmět: |
rhamnogalacturonan II
Arabidopsis Proteins arabidopsis thaliana Arabidopsis arabinogalactan-proteins Cell Biology Biochemistry Catalysis Peptide Fragments borate diester bridges Mucoproteins Lead Cell Wall Cations Borates Rhamnogalacturonans plant cell wall pectic polysaccharide Molecular Biology Boron Plant Proteins |
| Zdroj: | Sanhueza, D, Begum, R A, Albenne, C, Jamet, E & Fry, S C 2022, ' An Arabidopsis thaliana arabinogalactan-protein (AGP31) and several cationic AGP fragments catalyse the boron bridging of rhamnogalacturonan-II ', Biochemical Journal, vol. 479, no. 18, BCJ20220340, pp. 1967-1984 . https://doi.org/10.1042/BCJ20220340 |
| ISSN: | 1470-8728 0264-6021 |
| Popis: | Rhamnogalacturonan-II (RG-II) is a complex pectic domain in plant primary cell walls. In vivo, most RG-II domains are covalently dimerised via borate diester bridges, essential for correct cell-wall assembly, but the dimerisation of pure RG-II monomers by boric acid in vitro is extremely slow. Cationic ‘chaperones’ can promote dimerisation, probably by overcoming the mutual repulsion between neighbouring anionic RG-II molecules. Highly effective artificial chaperones include Pb2+ and polyhistidine, but the proposed natural chaperones remained elusive. We have now tested cationic peptide fragments of several Arabidopsis thaliana arabinogalactan-proteins (AGPs) as candidates. Fragments of AGP17, 18, 19 and 31 were effective, typically at ∼25 µg/ml (9–19 µM), promoting the boron bridging of 16–20 µM monomeric RG-II at pH 4.8 in vitro. Native AGP31 glycoprotein was also effective, and hexahistidine was moderately so. All chaperones tested interacted reversibly with RG-II and were not consumed during the reaction; thus they acted catalytically, and may constitute the first reported boron-acting enzyme activity, an RG-II borate diesterase. Many of the peptide chaperones became less effective catalysts at higher concentration, which we interpret as due to the formation of RG-II–peptide complexes with a net positive charge, as mutually repulsive as negatively charged pure RG-II molecules. The four unique AGPs studied here may serve an enzymic role in the living plant cell, acting on RG-II within Golgi cisternae and/or in the apoplast after secretion. In this way, RG-II and specific AGPs may contribute to cell-wall assembly and hence plant cell expansion and development. |
| Databáze: | OpenAIRE |
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