The calcium-binding protein CSE links Ca(2+) signaling with cell-cell communication in cyanobacteria.

CSE, a calcium-binding protein, is essential for cell-cell communication and septal junction formation in multicellular cyanobacteria, linking calcium signaling to multicellularity.

• Why it matters: Understanding how calcium signaling influences cell communication in cyanobacteria fills a knowledge gap about the regulation of multicellularity in prokaryotes and its evolutionary conservation.
• What they did: Researchers determined the NMR structure of CSE in its calcium-bound form and used cryo-electron tomography to compare mutant and wild-type cells, revealing CSE’s role in junction formation.
• The result: CSE regulates septal junctions and nanopores, enabling cell communication, and underscores calcium signaling as a conserved mechanism for cellular junction regulation across diverse organisms.