Members of this family are found in Myrmecia pilosula and represent a group of peptides that display cytotoxic, hypotensive, histamine-releasing and antimicrobial activities. Pilosulins constitute the major allergens of the venom of Myrmecia pilosula (Myrmeciinae). Pilosulin 1 is a long linear peptide (57 amino acids) and displays haemolytic and cytolytic activities. Pilosulins 3, 4, and 5 are a group of homo- and heterodimeric peptides [1]. Pilosulin 1 Swiss:Q07932 is expressed in the venom sac of ants in the form of a propeptide (112 kDa) which undergoes extensive post-translational modification. It is proposed to give rise to a family of six homologous C-terminal peptide sub-sequences containing between 27 and 56 amino acid residues in the final venom. Furthermore, it is found to form random coils and have minimal secondary structure. However, in increasingly hydrophobic conditions, approximately one-third of the peptide forms alpha-helix secondary structures. Studies on human erythrocytes and lymphocytes, show that Pilosulin 1 is highly lytic towards leukocytes and that the NH2-terminus (20 N-terminal residues) of Pilosulin 1 is critical for its cytotoxic activity and antimicrobial activities. Another family member Pilosulin 3 Swiss:Q68Y23, is a heterodimer of Pilosulin 3a and Pilosulin 3b linked in anti-parallel fashion through 2 disulfide bridges. This peptide is the most abundant peptide found in native venom [2].

1: The Biochemical Toxin Arsenal from Ant Venoms. Touchard A, Aili SR, Fox EG, Escoubas P, Orivel J, Nicholson GM, Dejean A; Toxins (Basel). 2016; [Epub ahead of print] PMID:26805882

2: Pilosulins: a review of the structure and mode of action of venom peptides from an Australian ant Myrmecia pilosula. Wanandy T, Gueven N, Davies NW, Brown SG, Wiese MD; Toxicon. 2015;98:54-61. PMID:25725257