ExeM, as described in Shewanella oneidensis, is a biofilm formation-associated exonuclease that cleaves extracellular DNA (eDNA), a biofilm component. Members of the ExeM family contain two or three pairs of Cys residues, presumed to form disulfide bonds, and a C-terminal GlyGly-CTERM membrane-anchoring segment. Strangely, engineered removal of the GlyGly-CTERM region did not result in net export from the cell and appearance of the enzyme in culture supernatants.
Jiyao W et al.(2023). "The conserved domain database in 2023.",