The members of this family are short cysteine-rich membrane proteins that most probably dimerize together to form a transmembrane sulfhydryl-lined pore. The CYSTM module is always present at the extreme C-terminus of the protein in which it is present. Furthermore, like the yeast prototypes, the majority of the proteins also possess a proline/glutamine-rich segment upstream of the CYSTM module that is likely to form a polar, disordered head in the cytoplasm. The presence of an atypical well-conserved acidic residue at the C-terminal end of the TM helix suggests that this might interact with a positively charged moiety in the lipid head group. Consistently across the eukaryotes, the different versions of the CYSTM module appear to have roles in stress-response or stress-tolerance, and, more specifically, in resistance to deleterious substances, implying that these might be general functions of the whole family.