Molecular Mechanisms Associated with Xylan Degradation by Xanthomonas Plant Pathogens
| Autor: | Leandro H.P. Assis, Letícia Maria Zanphorlin, Roberto Ruller, Rodrigo V. Honorato, Mário T. Murakami, Vanesa Peixoto de Matos Martins, Paulo S. L. Oliveira, Camila R. Santos, Zaira B. Hoffmam |
|---|---|
| Rok vydání: | 2014 |
| Předmět: |
Xanthomonas
Glycoside Hydrolases Molecular Sequence Data Oligosaccharides Calorimetry Crystallography X-Ray Protein Engineering Biochemistry Bacterial Proteins Cell Wall Glycoside hydrolase Amino Acid Sequence Cloning Molecular Mode of action Molecular Biology Peptide sequence Ions Endo-1 4-beta Xylanases Sequence Homology Amino Acid biology Effector beta-Glucosidase Temperature Cell Biology Protein engineering Plants biology.organism_classification Xylan Protein Structure and Folding Carbohydrate Metabolism Calcium Xylans Protein Multimerization Bacterial outer membrane |
| Zdroj: | Journal of Biological Chemistry. 289:32186-32200 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m114.605105 |
| Popis: | Xanthomonas pathogens attack a variety of economically relevant plants, and their xylan CUT system (carbohydrate utilization with TonB-dependent outer membrane transporter system) contains two major xylanase-related genes, xynA and xynB, which influence biofilm formation and virulence by molecular mechanisms that are still elusive. Herein, we demonstrated that XynA is a rare reducing end xylose-releasing exo-oligoxylanase and not an endo-β-1,4-xylanase as predicted. Structural analysis revealed that an insertion in the β7-α7 loop induces dimerization and promotes a physical barrier at the +2 subsite conferring this unique mode of action within the GH10 family. A single mutation that impaired dimerization became XynA active against xylan, and high endolytic activity was achieved when this loop was tailored to match a canonical sequence of endo-β-1,4-xylanases, supporting our mechanistic model. On the other hand, the divergent XynB proved to be a classical endo-β-1,4-xylanase, despite the low sequence similarity to characterized GH10 xylanases. Interestingly, this enzyme contains a calcium ion bound nearby to the glycone-binding region, which is required for catalytic activity and structural stability. These results shed light on the molecular basis for xylan degradation by Xanthomonas and suggest how these enzymes synergistically assist infection and pathogenesis. Our findings indicate that XynB contributes to breach the plant cell wall barrier, providing nutrients and facilitating the translocation of effector molecules, whereas the exo-oligoxylanase XynA possibly participates in the suppression of oligosaccharide-induced immune responses. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|