Plant cell walls are highly complex structures of interlocking polysaccharides that are recalcitrant to biological degradation. Within the complex molecular machinery involved in its deconstruction, one of the greatest challenges is to decipher the mechanism that display enzymes with multiple copies of ancillary non-catalytic domains. Most of these domains are Carbohydrate Binding Modules (CBMs). Homogeneous multimodularity has been related to multivalency and avidity effects, while heterogeneous pattern is supposed to provide distinct substrate-binding specificities. However, recent work suggests that this panorama may be more complex. Researchers at IQFR have performed structural and functional studies on a large xylanase (Xyn10c) showing a distinctive modular structure that contains an N-terminal tandem of two CBM22s and a duplicated CMB9 at its C-terminus. We have discovered novel features that attribute a different functionality to each CBM22 module and suggest a deliver strategy of Xyn10C mediated by its CBM22 tandem. Our work will contribute to unravel the mechanisms ruling modularity, which is essential to understand the biomass recycling and to produce efficient biocatalysts. This will result in more environmentally sustainable industries.

The Journal of Biological Chemistry (2015)
First published in May 22
(doi:10.1074/jbc.M115.659300)