TY  - JOUR
A1  - Deschamps, Philippe
A1  - Haferkamp, Ilka
A1  - Dauvillee, David
A1  - Haebel, Sophie
A1  - Steup, Martin
A1  - Buleon, Alain
A1  - Putaux, Jean-Luc
A1  - Colleoni, Christophe
A1  - d'Hulst, Christophe
A1  - Plancke, Charlotte
A1  - Gould, Sven
A1  - Maier, Uwe
A1  - Neuhaus, Heinz Eckhard
A1  - Ball, Steven G.
T1  - Nature of the periplastidial pathway of starch synthesis in the cryptophyte Guillardia theta
N2  - The nature of the periplastidial pathway of starch biosynthesis was investigated with the model cryptophyte Guillardia theta. The storage polysaccharide granules were shown to be composed of both amylose and amylopectin fractions with a chain length distribution and crystalline organization very similar to those of starch from green algae and land plants. Most starch granules displayed a shape consistent with biosynthesis occurring around the pyrenoid through the rhodoplast membranes. A protein with significant similarity to the amylose-synthesizing granule-bound starch syntbase 1 from green plants was found as the major polypeptide bound to the polysaccharide matrix. N-terminal sequencing of the mature protein proved that the precursor protein carries a nonfunctional transit peptide in its bipartite topogenic signal sequence which is cleaved without yielding transport of the enzyme across the two inner plastid membranes. The enzyme was shown to display similar affinities for ADP and UDP-glucose, while the V-max measured with UDP-glucose was twofold higher. The granule-bound starch synthase from Guillardia theta was demonstrated to be responsible for the synthesis of long glucan chains and therefore to be the functional equivalent of the amylose- synthesizing enzyme of green plants. Preliminary characterization of the starch pathway suggests that Guillardia theta utilizes a UDP-glucose-based pathway to synthesize starch
Y1  - 2006
UR  - http://ec.asm.org/
U6  - https://doi.org/10.1128/Ec.00380-05
SN  - 1535-9778
ER  -