Figure 1 - full size

Figure 1. Figure 1. (a) Diagram of conserved intein motifs of bifunctional inteins, mini inteins and the Ssp DnaE split intein. Blocks A and B (black) in the N-terminal subdomain (magenta) and blocks F and G (black) in the C-terminal subdomain (yellow) are shared by the splicing domains and the endonuclease domain is shown in grey. Residues involved in nucleophilic attack (letters in a box), as well as other highly conserved amino acids are indicated below the block diagram. (b) A representation of the Ssp DnaE intein fusions. The exDnaE fusion protein consists of maltose-binding protein (MBP), the full-length wild-type Ssp DnaE intein (residues 1-159, which include 123 amino acid residues from the N terminus and 36 amino acid residues from the C terminus) with five native extein residues at its N terminus and three native residues at its C terminus, and the CBD. The resulting protein exDnaE is splicing functional. Black arrows indicate the splicing sites of Ssp DnaE intein. preDnaE consists of CBD, Ssp DnaB intein and the full-length Ssp DnaE intein with C1A and N159A mutations (residue 1-159) along with five native extein residues at its N terminus and three native residues at its C terminus. The black arrow shows the cleavage site of the modified Ssp DnaB intein.41 The intein proteins after purification are indicated in red.