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Title: Distinct roles of N- and O-glycans in cellulase activity and stability

In nature, many microbes secrete mixtures of glycoside hydrolases, oxidoreductases, and accessory enzymes to deconstruct polysaccharides and lignin in plants. These enzymes are often decorated with N- and O-glycosylation, the roles of which have been broadly attributed to protection from proteolysis, as the extracellular milieu is an aggressive environment. Glycosylation has been shown to sometimes affect activity, but these effects are not fully understood. In this paper, we examine N- and O-glycosylation on a model, multimodular glycoside hydrolase family 7 cellobiohydrolase (Cel7A), which exhibits an O-glycosylated carbohydrate-binding module (CBM) and an O-glycosylated linker connected to an N- and O-glycosylated catalytic domain (CD) - a domain architecture common to many biomass-degrading enzymes. We report consensus maps for Cel7A glycosylation that include glycan sites and motifs. Additionally, we examine the roles of glycans on activity, substrate binding, and thermal and proteolytic stability. N-glycan knockouts on the CD demonstrate that N-glycosylation has little impact on cellulose conversion or binding, but does have major stability impacts. O-glycans on the CBM have little impact on binding, proteolysis, or activity in the whole-enzyme context. However, linker O-glycans greatly impact cellulose conversion via their contribution to proteolysis resistance. Molecular simulations predict an additional role for linker O-glycans,more » namely that they are responsible for maintaining separation between ordered domains when Cel7A is engaged on cellulose, as models predict a-helix formation and decreased cellulose interaction for the nonglycosylated linker. In conclusion, this study reveals key roles for N- and O-glycosylation that are likely broadly applicable to other plant cell-wall-degrading enzymes.« less
Authors:
 [1] ;  [2] ; ORCiD logo [3] ;  [3] ;  [3] ;  [3] ;  [3] ;  [2] ;  [1] ;  [1] ;  [1] ;  [1] ; ORCiD logo [4] ;  [1] ;  [1] ; ORCiD logo [1] ; ORCiD logo [2] ;  [1]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States). Biosciences Center
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Bioenergy Center
  3. Univ. of Georgia, Athens, GA (United States). Complex Carbohydrate Research Center
  4. Univ. of Colorado, Boulder, CO (United States). Department of Chemistry and Biochemistry and BioFrontiers Institute
Publication Date:
Report Number(s):
NREL/JA-5100-70178
Journal ID: ISSN 0027-8424
Grant/Contract Number:
AC36-08GO28308; SC0015662
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 52; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Bioenergy Technologies Office (EE-3B); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; 54 ENVIRONMENTAL SCIENCES; 09 BIOMASS FUELS; glycoside hydrolase; glycosylation; linker; intrinsically disordered protein; mannosylation; cellulase
OSTI Identifier:
1417800

Amore, Antonella, Knott, Brandon C., Supekar, Nitin T., Shajahan, Asif, Azadi, Parastoo, Zhao, Peng, Wells, Lance, Linger, Jeffrey G., Hobdey, Sarah E., Vander Wall, Todd A., Shollenberger, Todd, Yarbrough, John M., Tan, Zhongping, Crowley, Michael F., Himmel, Michael E., Decker, Stephen R., Beckham, Gregg T., and Taylor, Larry E.. Distinct roles of N- and O-glycans in cellulase activity and stability. United States: N. p., Web. doi:10.1073/pnas.1714249114.
Amore, Antonella, Knott, Brandon C., Supekar, Nitin T., Shajahan, Asif, Azadi, Parastoo, Zhao, Peng, Wells, Lance, Linger, Jeffrey G., Hobdey, Sarah E., Vander Wall, Todd A., Shollenberger, Todd, Yarbrough, John M., Tan, Zhongping, Crowley, Michael F., Himmel, Michael E., Decker, Stephen R., Beckham, Gregg T., & Taylor, Larry E.. Distinct roles of N- and O-glycans in cellulase activity and stability. United States. doi:10.1073/pnas.1714249114.
Amore, Antonella, Knott, Brandon C., Supekar, Nitin T., Shajahan, Asif, Azadi, Parastoo, Zhao, Peng, Wells, Lance, Linger, Jeffrey G., Hobdey, Sarah E., Vander Wall, Todd A., Shollenberger, Todd, Yarbrough, John M., Tan, Zhongping, Crowley, Michael F., Himmel, Michael E., Decker, Stephen R., Beckham, Gregg T., and Taylor, Larry E.. 2017. "Distinct roles of N- and O-glycans in cellulase activity and stability". United States. doi:10.1073/pnas.1714249114.
@article{osti_1417800,
title = {Distinct roles of N- and O-glycans in cellulase activity and stability},
author = {Amore, Antonella and Knott, Brandon C. and Supekar, Nitin T. and Shajahan, Asif and Azadi, Parastoo and Zhao, Peng and Wells, Lance and Linger, Jeffrey G. and Hobdey, Sarah E. and Vander Wall, Todd A. and Shollenberger, Todd and Yarbrough, John M. and Tan, Zhongping and Crowley, Michael F. and Himmel, Michael E. and Decker, Stephen R. and Beckham, Gregg T. and Taylor, Larry E.},
abstractNote = {In nature, many microbes secrete mixtures of glycoside hydrolases, oxidoreductases, and accessory enzymes to deconstruct polysaccharides and lignin in plants. These enzymes are often decorated with N- and O-glycosylation, the roles of which have been broadly attributed to protection from proteolysis, as the extracellular milieu is an aggressive environment. Glycosylation has been shown to sometimes affect activity, but these effects are not fully understood. In this paper, we examine N- and O-glycosylation on a model, multimodular glycoside hydrolase family 7 cellobiohydrolase (Cel7A), which exhibits an O-glycosylated carbohydrate-binding module (CBM) and an O-glycosylated linker connected to an N- and O-glycosylated catalytic domain (CD) - a domain architecture common to many biomass-degrading enzymes. We report consensus maps for Cel7A glycosylation that include glycan sites and motifs. Additionally, we examine the roles of glycans on activity, substrate binding, and thermal and proteolytic stability. N-glycan knockouts on the CD demonstrate that N-glycosylation has little impact on cellulose conversion or binding, but does have major stability impacts. O-glycans on the CBM have little impact on binding, proteolysis, or activity in the whole-enzyme context. However, linker O-glycans greatly impact cellulose conversion via their contribution to proteolysis resistance. Molecular simulations predict an additional role for linker O-glycans, namely that they are responsible for maintaining separation between ordered domains when Cel7A is engaged on cellulose, as models predict a-helix formation and decreased cellulose interaction for the nonglycosylated linker. In conclusion, this study reveals key roles for N- and O-glycosylation that are likely broadly applicable to other plant cell-wall-degrading enzymes.},
doi = {10.1073/pnas.1714249114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 52,
volume = 114,
place = {United States},
year = {2017},
month = {12}
}

Works referenced in this record:

Revealing Nature's Cellulase Diversity The Digestion Mechanism of Caldicellulosiruptor bescii CelA
journal, December 2013