Crystal structures of a poplar xyloglucan endotransglycosylase reveal details of the transglycosylation acceptor binding
2004 (English)In: The Plant Cell, ISSN 1040-4651, E-ISSN 1532-298X, Vol. 16, no 4, 874-886 p.Article in journal (Refereed) Published
Xyloglucan endotransglycosylases (XETs) cleave and religate xyloglucan polymers in plant cell walls via a transglycosylation mechanism. Thus, XET is a key enzyme in all plant processes that require cell wall remodeling. To provide a basis for detailed structure-function studies, the crystal structure of Populus tremula x tremuloides XET16A (PttXET16A), heterologously expressed in Pichia pastoris, has been determined at 1.8-Angstrom resolution. Even though the overall structure of PttXET16A is a curved beta-sandwich similar to other enzymes in the glycoside hydrolase family GH16, parts of its substrate binding cleft are more reminiscent of the distantly related family GH7. In addition, XET has a C-terminal extension that packs against the conserved core, providing an additional beta-strand and a short alpha-helix. The structure of XET in complex with a xyloglucan nonasaccharide, XLLG, reveals a very favorable acceptor binding site, which is a necessary but not sufficient prerequisite for transgilycosylation. Biochemical data imply that the enzyme requires sugar residues in both acceptor and donor sites to properly orient the glycosidic bond relative to the catalytic residues.
Place, publisher, year, edition, pages
2004. Vol. 16, no 4, 874-886 p.
PLANT-CELL WALL; TRICHODERMA-REESEI; CELLOBIOHYDROLASE-I; MACROMOLECULAR STRUCTURES; GLYCOSIDE HYDROLASES; ARABIDOPSIS ROOTS; DONOR SUBSTRATE; ACTIVE-SITE; OLIGOSACCHARIDES; NOMENCLATURE
IdentifiersURN: urn:nbn:se:kth:diva-6912DOI: 10.1105/tpc.020065ISI: 000220731900010ScopusID: 2-s2.0-1842813472OAI: oai:DiVA.org:kth-6912DiVA: diva2:11758
QC 201006242007-03-222007-03-222012-03-22Bibliographically approved