Open reading frames around the cwlP region and domain structure of CwlP. The cwlP gene is located between the yomK-yomJ operon and yomH-yomG operon in the SP-β region (2). yomK, yomJ, yomH, and yomG genes have unknown functions. CwlP consists of 2,285 amino acids residues, and at least three domains have been classified in the Pfam database. These include a phage-related minor tail protein (shaded box), an SLT domain (black box, which is actually a muramidase domain), and a peptidase M23 domain (dark gray box, dd-endopeptidase domain). Numbers indicate the positions of amino acid residues from the first amino acid, Met, of CwlP. The purified proteins, CwlP-SLT, CwlP-M23, CwlP-SLTM23, and full-length CwlP, were shown to have these domain structures.