In Metazoa, the main actors of apoptosis are proteases termed caspases. Unexpectedly, genes coding for structurally homologous proteins were recently identified also in prokaryotes and are especially abundant in Cyanobacteria [Asplund-Samuelsson et al., 2012].
We have been the first to biochemically characterize these proteins and have due to their catalytic properties and evolutionary early emergence termed them orthocaspases [Klemencic et al., 2015].
As opposed to higher plants or animals, some algae and majority of cyanobacteria contain also proteins, that instead of the catalytic domain contain proteolytically inactive variants, they are therefore pseudo-enzymes. We recently reported their distribution in prokaryotic organisms [Klemencic et al., 2019]. To study the function of these proteins in vitro as well as in vivo, we are constructing genetically modified variants of orthocaspases in our two model cyanobacteria: Microcystis aeruginosa PCC 7806, which contains six different orthocaspase genes and Synechocystis sp. PCC 6803, containing only one pseudo-orthocaspase.
