Orthocaspases

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].

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Orthocaspase MaOC1 requires autoprpcessing to separate the p20 domain from the rest of the polypeptide chain for its activity.

 

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.

 

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