Standard numbering schemes
For the N- and C-terminal expansin domains, standard numbering schemes were introduced to annotate equivalent positions38. The B. subtilis expansin, Bs EXLX1 (PDB entry 4fer), was used as the reference sequence for the assignment of standard position numbers to the sequence entries in the ExED upon alignment against the respective profile HMM and subsequent transfer of position numbers: For both expansin domains, the standard positions range from 11 to 105 and 114 to 186. Insertions with respect to the reference sequence, such as loops, were specified by subsequent decimals. Thus, all position numbers mentioned herein are based on the reference Bs EXLX1, unless otherwise stated. Due to insertions in the reference sequence ofBs EXLX1, some regions in the underlying multiple sequence alignments of the standard numbering schemes appeared inaccurate, i.e. these regions could not be aligned properly: In the N-terminal expansin domain, inaccurate positions are from 14.1 to 17, 39.1 to 47, and 104.1 to 105; in the C-terminal expansin domain, inaccurate positions are from 162.1 to 164 and 185.1 to 186.