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Publication Abstract from PubMed

Elucidating the molecular mechanisms regulating multimodularity is a challenging task. Paenibacillus barcinonensis Xyn10C is a 120 kD modular enzyme that presents the CBM22/GH10/CBM9 architecture found in a subset of large xylanases. We report here the three-dimensional structure of the Xyn10C N-terminal region, containing the xylan-binding CBM22-1-CBM22-2 tandem (Xyn10C-XBD), which represents the first solved crystal structure of two contiguous CBM22. Xyn10C-XBD is folded into two separate CBM22 modules linked by a flexible segment that endows the tandem with extraordinary plasticity. Each isolated domain have been expressed and crystallized and their binding abilities have been investigated. Both domains contain the RW/YYYE motif required for xylan binding. However, crystallographic analysis of CBM22-2 complexes shows Trp308 as an additional binding determinant. The long loop containing Trp308 creates a platform that possibly contributes to recognize precise decorations at subsite S2. CBM22-2 may thus define a subset of xylan-binding CBM22s directed to particular regions of the polysaccharide. Affinity electrophoresis reveals Xyn10C-XBD binds arabinoxylans more tightly, more apparent when CBM22-2 is tested against highly substituted xylan. The crystal structure of the catalytic domain, also reported, shows the capacity of the active site to accommodate xylan substitutions at almost all subsites. The structural differences found at both Xyn10C-XBD domains are consistent with the ITC experiments showing two sites with different affinities in the tandem. On the basis of the CBM22 distinct characteristics, a deliver strategy of Xyn10C mediated by Xyn10C-XBD is proposed.

Exploring multimodularity in plant cell wall deconstruction: structural and functional analysis of Xyn10C containing the CBM22-1-CBM22-2 tandem.,Sainz-Polo MA, Gonzalez B, Menendez M, Pastor FI, Sanz-Aparicio J J Biol Chem. 2015 May 22. pii: jbc.M115.659300. PMID:26001782^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.