The SPOR domain is named after the founding member of the protein family, a Bacillus subtilis cell wall amidase named CwlC that is produced relatively late in the process of sporulation. SPOR domain proteins are widespread in bacteria, many of these proteins are involved in sporulation and cell division, and SPOR domains are sufficient for septal localization, probaly because SPOR domains bind to septal peptidoglycan (PG) [1,2,3,4,5].

The SPOR domain is ~75 amino acid long. It comprises two tandem repeats that fold into a pseudo-2-fold symmetric single-domain structure consisting of a βαββαβ-fold containing numerous contacts between the repeats (see <PDB:1X60>). Hydrophobic residues important for structural integrity are conserved between the repeats, and are located symmetrically. The SPOR domain assembles into a four-stranded antiparallel β-sheet buttressed on one side by two α-helices [1,2,5].

Some proteins kwown to contain a SPOR domain are listed below:

• Bacteria CwlC, a sporulation protein which comprises an N-terminal amidase domain and a C-terminal SPOR domain. It facilitates release of the mature spore by degrading PG in the mother cell.
• Bacteria DamX, a bitopic inner membrane division protein.
• Bacteria FtsN, a bitopic inner membrane protein essential for cell division.
• Bacteria DedD, a bitopic inner membrane protein that contributes to the cell constriction process.
• Bacteria RlpA, a predicted outer membrane lipoprotein.

The profile we developed covers the entire SPOR domain.