This domain is found near the N-terminus of a variety of bacterial surface proteins and pili. This domain contains an unusual covalent ester bond between a conserved cysteine and glutamine residue [1].
This entry contains a prealbumin-like domain from a wide variety of bacterial surface proteins. This entry corresponds to domain 1 and domain 3 of SpaA from Corynebacterium diphtheriae [1]. Some members of this family contain an isopeptide bond.