Biochemical and Bioinformatic Characterization of Type II Metacaspase Protein (TaeMCAII) from Wheat

The biochemical analysis and homology modeling of a tertiary structure of a cereal type II metacaspase protein from wheat (Triticum aestivum), TaeMCAII, are presented. The biochemical characterization of synthetic oligopeptides and protease inhibitors of Escherichia coli-produced and purified recombinant TaeMCAII revealed that this metacaspase protein, similar to other known plant metacaspases, is an arginine/lysine-specific cysteine protease. Thus, a model of a plant type II metacaspase structure based on newly identified putative metacaspase-like template was proposed. Homology modeling of the TaeMCAII active site tertiary structure showed two cysteine residues, Cys140 and 23, in close proximity to the catalytic histidine, most likely participating in proton exchange during the catalytic process. The autoprocessing that leads to activation of TaeMCAII was highly dependent on Cys140. TaeMCAII required high levels of calcium ions for activity, which could indicate its involvement in stress signaling pathways connected to programmed cell death.