This is a family of sequences found in both bacteria and bacteriophages. This region is approximately 130 residues long and in some cases is found as part of the PVL (Panton-Valentine leukocidin) group of genes, which encode a member of the leukocidin group of bacterial toxins that kill leukocytes by creation of pores in the cell membrane [1]. PVL appears to be a virulence factor associated with a number of human diseases [2].

1: Genome and virulence determinants of high virulence community-acquired MRSA. Baba T, Takeuchi F, Kuroda M, Yuzawa H, Aoki K, Oguchi A, Nagai Y, Iwama N, Asano K, Naimi T, Kuroda H, Cui L, Yamamoto K, Hiramatsu K; Lancet 2002;359:1819-1827. PMID:12044378

2: Involvement of Panton-Valentine leukocidin-producing Staphylococcus aureus in primary skin infections and pneumonia. Lina G, Piemont Y, Godail-Gamot F, Bes M, Peter MO, Gauduchon V, Vandenesch F, Etienne J; Clin Infect Dis 1999;29:1128-1132. PMID:10524952