Fig. 7
Structural evidence that compost21_GH11 is an exo-1,4-β-xylanase. a Amino acid sequence multiple alignment of compost21_GH11 with closest homologues selected based on searches in the NCBI-nr and PDB databases. The residues responsible for formation of extra loops 1 and 2 (EL1 and EL2) are shown in a red box while the catalytic residues are marked in a blue box. The extra loops are present in other proteins for which structure has not been solved. b Overall secondary structure of compost21_GH11 colored from blue to red (N- to C-terminal). c Superposition of all available GH11 structures (in gray) with compost21_GH11 (in magenta). The orientation of the structures is rotated by 90° in relation to the structure presented on item B. The non-aligned domains from proteins with non-common domains were hidden from representation. d Surface representation of compost21_GH11 (in magenta) aligned to closest PDB homologue 1XNK (in gray). Note that the non-reducing end of the ligand methyl 4,4II-dithio-α-xylotrioside present in 1XNK structure is sterically hindered by EL2 in compost21_GH11 − 3 subsite