| Autor: |
Liu C; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Pfister B; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Osman R; Université de Lille, CNRS, UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, Lille, France., Ritter M; Institute for Building Materials, ETH Zurich, Stefano-Franscini-Platz 3, 8093 Zurich, Switzerland., Heutinck A; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Sharma M; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Eicke S; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Fischer-Stettler M; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Seung D; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Bompard C; Université de Lille, CNRS, UMR 8576-UGSF-Unité de Glycobiologie Structurale et Fonctionnelle, Lille, France., Abt MR; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland., Zeeman SC; Institute of Molecular Plant Biology, ETH Zurich, Universitätstrasse 2, 8092 Zurich, Switzerland. |
| Abstrakt: |
Starch, the most abundant carbohydrate reserve in plants, primarily consists of the branched glucan amylopectin, which forms semi-crystalline granules. Phase transition from a soluble to an insoluble form depends on amylopectin architecture, requiring a compatible distribution of glucan chain lengths and a branch-point distribution. Here, we show that two starch-bound proteins, LIKE EARLY STARVATION 1 (LESV) and EARLY STARVATION 1 (ESV1), which have unusual carbohydrate-binding surfaces, promote the phase transition of amylopectin-like glucans, both in a heterologous yeast system expressing the starch biosynthetic machinery and in Arabidopsis plants. We propose a model wherein LESV serves as a nucleating role, with its carbohydrate-binding surfaces helping align glucan double helices to promote their phase transition into semi-crystalline lamellae, which are then stabilized by ESV1. Because both proteins are widely conserved, we suggest that protein-facilitated glucan crystallization may be a general and previously unrecognized feature of starch biosynthesis. |
