Heterologous Expression of MBP-AtABC1K6-His in E. coli

Heterologous E. coli expression of AtABC1K6 tagged with maltose binding protein (MBP) and 6xHis tags revealed a spontaneous cleavage event of the recombinant protein during purification. Resulting bands were resolved on SDS-PAGE and excised for MS/MS identification. Mass spec-based identification of the individual bands determined the cleavage event as ocurring after Lysine-443. The results demonstrate that the resulting ca. 80 kD band, showing kinase activity, comprises the AtABC1K6-6xHis fragment lacking the first 71 residues of AtABC1K6.