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Analysis of nasturtium TmNXG1 complexes by crystallography and molecular dynamics provides detailed insight into substrate recognition by family GH16 xyloglucan endo-transglycosylases and endo-hydrolases
KTH, School of Biotechnology (BIO), Glycoscience.
KTH, School of Biotechnology (BIO), Glycoscience.
KTH, School of Biotechnology (BIO), Glycoscience.
KTH, School of Biotechnology (BIO), Glycoscience.
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2009 (English)In: Proteins: Structure, Function, and Genetics, ISSN 0887-3585, E-ISSN 1097-0134, Vol. 75, no 4, 820-836 p.Article in journal (Refereed) Published
Abstract [en]

Reorganization and degradation of the wall crosslinking and seed storage polysaccharide xyloglucan by glycoside hydrolase family 16 (GH16) endo-transglycosylases and hydrolases are crucial to the growth of the majority of land plants, affecting processes as diverse as germination, morphogenesis, and fruit ripening. A high-resolution, three-dimensional structure of a nasturtium (Tropaeolum majus) endo-xyloglucanase loop mutant, TmNXG1-Delta YNIIG, with an ohgosaccharide product bound in the negative active-site subsites, has been solved by X-ray crystallography. Comparison of this novel complex to that of the strict xyloglucan endotransglycosylase PttXET16-34 from hybrid aspen (Populus tremula x tremuloides), previously solved with a xylogluco-oligosaccharide bound in the positive subsites, highlighted key protein structures that affect the disparate catalytic activities displayed by these closely related enzymes. Combination of these "partial" active-site complexes through molecular dynamics simulations in water allowed modeling of wild-type TmNXG1, TmNXG1-Delta YNIIG, and wild-type PttXET16-34 in complex with a xyloglucan octadecasaccharide spanning the entire catalytic cleft. A comprehensive analysis of these full-length complexes underscored the importance of various loops lining the active site. Subtle differences leading to a tighter hydrogen bonding pattern on the negative (glycosyl donor) binding subsites, together with loop flexibility on the positive (glycosyl acceptor) binding subsites appear to favor hydrolysis over transglycosylation in GH16 xyloglucan-active enzymes.

Place, publisher, year, edition, pages
2009. Vol. 75, no 4, 820-836 p.
Keyword [en]
xyloglucan, nasturtium seedlings, cell wall polysaccharides, crystal, structure, molecular dynamics, cell-walls, glycoside hydrolases, crystal-structures, oligosaccharides, endotransglycosylase, nomenclature, acceptor, perspectives, degradation, cotyledons
URN: urn:nbn:se:kth:diva-18433DOI: 10.1002/prot.22291ISI: 000266133600004ScopusID: 2-s2.0-66149174788OAI: diva2:336480
QC 20100902Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2010-09-02Bibliographically approved
In thesis
1. On the engineering of proteins: methods and applications for carbohydrate-active enzymes
Open this publication in new window or tab >>On the engineering of proteins: methods and applications for carbohydrate-active enzymes
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents the application of different protein engineering methods on enzymes and non-catalytic proteins that act upon xyloglucans. Xyloglucans are polysaccharides found as storage polymers in seeds and tubers, and as cross-linking glucans in the cell wall of plants. Their structure is complex with intricate branching patterns, which contribute to the physical properties of the polysaccharide including its binding to and interaction with other glucans such as cellulose.

One important group of xyloglucan-active enzymes is encoded by the GH16 XTH gene family in plants, including xyloglucan endo-transglycosylases (XET) and xyloglucan endo-hydrolases (XEH). The molecular determinants behind the different catalytic routes of these homologous enzymes are still not fully understood. By combining structural data and molecular dynamics (MD) simulations, interesting facts were revealed about enzyme-substrate interaction. Furthermore, a pilot study was performed using structure-guided recombination to generate a restricted library of XET/XEH chimeras.

Glycosynthases are hydrolytically inactive mutant glycoside hydrolases (GH) that catalyse the formation of glycosidic linkages between glycosyl fluoride donors and glycoside acceptors. Different enzymes with xyloglucan hydrolase activity were engineered into glycosynthases, and characterised as tools for the synthesis of well-defined homogenous xyloglucan oligo- and polysaccharides with regular substitution patterns.

Carbohydrate-binding modules (CBM) are non-catalytic protein domains that bind to polysaccharidic substrates. An important technical application involves their use as molecular probes to detect and localise specific carbohydrates in vivo. The three-dimensional structure of an evolved xyloglucan binding module (XGBM) was solved by X-ray diffraction. Affinity-guided directed evolution of this first generation XGBM resulted in highly specific probes that were used to localise non-fucosylated xyloglucans in plant tissue sections.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xii, 74 p.
Trita-BIO-Report, ISSN 1654-2312 ; 2010:14
enzyme engineering, rational design, directed evolution, DNA shuffling, glycosynthase, xyloglucan, xyloglucan endo-transglycosylase, retaining glycoside hydrolase, xyloglucanase, carbohydrate binding module, polysaccharide synthesis
National Category
Industrial Biotechnology
urn:nbn:se:kth:diva-24296 (URN)978-91-7415-709-3 (ISBN)
Public defence
2010-09-22, FD5, AlbaNova Universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:15 (English)
QC 20100902Available from: 2010-09-02 Created: 2010-08-31 Last updated: 2010-09-02Bibliographically approved

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