Figure 4.

The effects of mutating conserved Dra Snf2 intein residues were examined. Mutated MIP precursors were expressed at 37°C for 2 h followed by 15°C overnight. Soluble proteins were electrophoresed in SDS-PAGE followed by staining with Coomassie Blue. Mutations are listed above each lane. Part A: splice junction residues, Part B: mutations in Blocks B and F, and Part C: mutations yielding branched intermediates. Multiple mutations in the same protein are separated by a slash. Abbreviations as in Figure 3 plus WT, wild type Dra Snf2 intein and “S,” 10–250 kDa Protein Ladder (250, 150, 100, 80, 60, 50, 40, 30, 25 kDa, where 80 and 25 kDa are darker bands).