Sequence conservation in the expansin superfamily. Sequence logos for the four expansin families were generated with WebLogo  and manually aligned. The signal peptide and the poorly conserved amino terminus of the mature proteins have been removed from the alignment; because some expansins have exceptionally large signal peptides and amino-terminal extensions the alignment starts around position 60. In these sequence logos the height of the stack of amino-acid symbols at each position indicates the degree of sequence conservation, and the height of each letter within the stack indicates the frequency of the corresponding amino acid. Residues conserved between families are shaded, and the boundary between the two domains is indicated by arrows. Key residues that are part of the catalytic site of GH45 proteins and that are conserved in domain 1 of some expansin families are shown in circles above the logos. EXPA, α-expansin; EXPB, β-expansin; EXLA, expansin-like A; EXLB, expansin-like B.