Conserved structural and sequence features of the ASRAH domain. A) Topology diagrams of Thermotoga TM1070 and the Rhodothermus marinus carbohydrate-binding module (CBM4-2) present in xylanase 10A. Equivalent strands are colored similarly. Numbers below each topology diagram illustrate the strand order. Note the circular permutation in the CBM4-2 domain. Additional N-terminal strands characteristic of CBM4-2 are colored orange. B) Cartoon representation of Thermotoga ASRAH homolog TM1070 (PDB: 1NC7), with key residue side-chains represented as sticks. Predicted ligand-binding residues are marked in green (H25 and C29), and other conserved residues (W7 and N32) in yellow. C) Surface model of the TM1070 tetramer, with the conserved histidine (H25) and cysteine (C29) of chain A marked in blue and yellow respectively. The 1,2-ethanediol molecule detected in the ligand-binding pocket of Thermotoga TM1070 is rendered as spheres. D) Comprehensive multiple sequence alignment of the ASRAH domain. Proteins are represented by their gene names, species abbreviations and gis. The coloring reflects the consensus at 70% conservation and highly conserved residues are shaded in red. Consensus abbreviations are listed in the lower panel. Refer to the Additional file 1 for species abbreviations.