Updated PubMed. Forisomes are giant polyprotein complexes that undergo an immense and fully reversible conformational change from a spindle into a plug-like state triggered by Ca2+ and pH changes. Resembling their native function in plant vasculature, forisomes can act as valves to efficiently regulate flow in microfluidic capillaries controlled by electro titration. Heterologous expression in yeast allows large scale production of tailor-made artificial forisomes which e.g. can be equipped with enzymes to generate bio-active surfaces. Herein, we analyzed the astonishing phenomenon of a disintegrating artificial forisome formed by truncated protein upon Ca2+ trigger, which opens new intriguing application perspectives of these protein polymers. We were able to assign this phenomenon to the lack of conserved motif M1 in the truncated MtSEO-F1 protein. Ambiguous redox states of four highly conserved cysteines within motif M1 and their participation in intra- and intermolecular disulfide bridges was identified by mass spectrometry analysis.