Structural and functional analysis of Aplysia attractins, a family of water-borne protein pheromones with interspecific attractiveness

Abstract

Mate attraction in Aplysia involves a long-distance water-borne signal (the protein pheromone attractin), which is released during egg laying. Aplysia californica attractin attracts species that produce closely related attractins, such as Aplysia brasiliana, whose geographic distribution does not overlap that of A. californica. This finding suggests that other mollusks release attractin-related pheromones to form and maintain breeding aggregations. We describe four additional members of the attractin family: A. brasiliana, Aplysia fasciata, Aplysia depilans (which aggregates with A. fasciata aggregations), and Aplysia vaccaria (which aggregates with A. californica aggregations). On the basis of their sequence similarity with A. californica attractin, the attractin proteins fall into two groups: A. californica, A. brasiliana, and A. fasciata (91-95% identity), and A. depilans and A. vaccaria (41-43% identity). The sequence similarity within the attractin family, the conserved six cysteines, and the compact fold of the NMR solution structure of A. californica attractin suggest a common fold for this pheromone family containing two antiparallel helices. The second helix contains the IEECKTS sequence conserved in Aplysia attractins. Mutating surface-exposed charged residues within this heptapeptide sequence abolishes attractin activity, suggesting that the second helix is an essential part of the receptor-binding interface.

Cold-adaptation in Sea-water-borne Signal Proteins: Sequence and NMR Structure of the Pheromone En-6 from the Antarctic Ciliate Euplotes nobilii

“…12 These data provided a platform for investigations of the functional biology of these molecules, 13,14 and led to the identification of structural relationships between the Er pheromones and another family of water-borne signal proteins, the "attractins", which control mate attraction and breeding aggregations in species of the marine gastropod Aplysia. 15,16 In spite of variations in their amino acid sequences, which contain from 37 to 40 residues, and in the acquisition of local specificities, the E. raikovi pheromones Er-1, Er-2, Er-10, Er-11 and Er-22 all share a common up-down-up three-helix bundle fold, which is covalently anchored by three strictly conserved disulfide bonds. Amazingly, this basic structural motif is also retained in a structurally deviant member of the Er family, Er-23, which has a polypeptide chain of 51 residues, forms an additional α-helix and contains two additional disulfide bonds.…”

Gender expression and group size: a test in a hermaphroditic and a gonochoric congeneric species of Ophryotrocha (Polychaeta)

“…in polychaetes (Hardege et al, 1998;Hardege and Bentley, 1997;Ram et al, 1999) and in corals (Twan et al, 2003)], and sperm activation and sperm attraction by eggs (Müller, 1976;Foltz, 1995). Hermaphroditic sea slugs of the genus Aplysia release a pheromone from their egg masses, which attracts potential mates and stimulates them to lay eggs on the same site (Painter et al, 2004). In hermaphroditic animals pheromones are also used to influence the fate of the donated sperm [e.g.…”

Snail odour-clouds: spreading and contribution to the transmission success of Trichobilharzia ocellata (Trematoda, Digenea) miracidia

“…Especially, chemical cues involved in predator avoidance have been subject of interest (Rittschof 1993;Burks and Lodge 2002;Leduc et al 2004), as well as the chemical ecology of snails in terms of their feeding habits and mate attraction (Thomas and Eaton 1993;Moomjian et al 2003;Webster et al 2003;Cummins et al 2004Cummins et al , 2005Painter et al 2004). Additionally, studies on trematode-snail interactions form a large research field including snail susceptibility and its mechanisms (Basch 1976;Sapp and Loker 2002;Theron et al 2004;Zhang et al 2004), as well as the chemical cues involved in miracidial and cercarial hostfinding (Saladin 1979;Haas and Haberl 1997;Sukhdeo and Sukhdeo 2004).…”