This family consists of the small acid-soluble spore protein (SASP) N type (sspN). SspN is a 48 residues protein that is expressed only in the forespore compartment of sporulating Bacillus subtilis. The sspN gene is recognized equally by both sigma-G and sigma-F. The role of SspN is still not well-defined.
Jiyao W et al.(2023). "The conserved domain database in 2023.",