Calpains in cyanobacteria and the origin of calpains

Area of Science:

• Biochemistry
• Molecular Biology
• Evolutionary Biology

Background:

• Calpains are a large superfamily of cysteine proteases crucial for numerous cellular functions.
• While extensively studied in mammals, calpain presence and function in bacteria remain largely unexplored.
• Archaea have not been found to possess calpains.

Purpose of the Study:

• To investigate the presence and evolutionary origins of calpains in cyanobacteria.
• To identify potential interaction partners for cyanobacterial calpains.
• To elucidate the evolutionary history of calpains across different domains of life.

Main Methods:

• In silico analyses were employed to identify calpains within selected cyanobacterial genomes.
• Protein-protein interaction analyses were performed to predict putative interaction partners.
• Phylogenetic analyses were conducted using calpain sequences from cyanobacteria, other bacteria, and eukaryotes.

Main Results:

• Calpains, characterized by the CysPC core domain, were identified in multiple cyanobacterial genera, including Anabaena, Microcystis, and others.
• Putative interaction partners for these cyanobacterial calpains were predicted through in silico analysis.
• Phylogenetic analysis revealed two distinct monophyletic clusters for bacterial and eukaryotic calpains.

Conclusions:

• The study confirms the presence of calpains in diverse cyanobacteria, expanding their known bacterial distribution.
• Phylogenetic data support two evolutionary scenarios: acquisition by eukaryotes from bacteria or ancient inheritance from a common ancestor with subsequent losses.
• Both scenarios necessitate multiple independent gene losses in various bacterial and eukaryotic lineages.