Conservation analyses
The two standard numbering schemes were used to analyze the amino acid
frequencies for the two expansin domains. The domains were annotated by
using hmmscan against all sequence entries of the ExED and
deploying the match criteria mentioned above. Each annotated domain
position was analyzed for conserved amino acids. Groups of amino acids
with similar biochemical properties, such as charge or polarity, were
also taken into account39,40. Conservation analyses
were performed separately for each superfamily of the ExED, and
additionally for EXPA, EXPB, EXLA (expansin-like A), and EXLB
(expansin-like B) (Tables S3 and S4 ). An amino acid
position was defined as conserved if it occurred in at least 70% of all
annotated sequence entries. Conserved positions were compared with the
positions in the structures of two bacterial expansins (PDB entries
4fer, chain B and 4jjo, chain A) and two plant expansins (PDB entries
1n10, chain A and 2hcz, chain X) to predict their functional relevance.