1.A.23.4.21
Very small MscS homolog of 109 aas with 1 or 2 TMSs, more similar to bacterial MscS proteins than to eukaryotic homologues.  The system has been characterized (Berg et al. 2024). Microsporidian genomes contain mscS genes of both eukaryotic and bacterial origin. Berg et al. 2024 investigated the cryo-electron microscopy structure of the bacterially derived mechanosensitive ion channel of small conductance 2 (MscS2) from Nematocida displodere, an intracellular pathogen of Caenorhabditis elegans. MscS2 is the most compact MscS-like channel known and assembles into a unique superstructure in vitro with six heptameric MscS2 channels. Individual MscS2 channels are oriented in a heterogeneous manner to one another, resembling an asymmetric, flexible six-way cross joint. Microsporidian MscS2 still forms a heptameric membrane channel.