Ataxin-1 AXH domain and DnaB intein domain: a. sequence alignment (colored according to similarity between residues) of Ataxin-1 AXH domain (SCOP ID: d1oa8a_) and DnaB intein domain (SCOP ID: d1mi8a_) by HHsearch. b. structure of Ataxin-1 AXH domain; the 6 β-strands from the evolutionary core are colored in rainbow and labeled with β1-β6 from N- to C-terminus. c. structure of DnaB intein domain; the evolutionary core is colored and labeled with β1-β6 and β1’-β6’ according to the structure of AXH domain in b. so that the corresponding secondary structure elements between two structures have the same color and label.