This family consists of the attractin family of water-borne pheromone. Mate attraction in Aplysia involves a long-distance water-borne signal in the form of the attractin peptide, that is released during egg laying. These peptides contain 6 conserved cysteines and are folded into 2 antiparallel helices. The second helix contains the IEECKTS sequence conserved in Aplysia attractins [1].

1: Structural and functional analysis of Aplysia attractins, a family of water-borne protein pheromones with interspecific attractiveness. Painter SD, Cummins SF, Nichols AE, Akalal DB, Schein CH, Braun W, Smith JS, Susswein AJ, Levy M, de Boer PA, ter Maat A, Miller MW, Scanlan C, Milberg RM, Sweedler JV, Nagle GT; Proc Natl Acad Sci U S A 2004;101:6929-6933. PMID:15118100