Abalone proteins

Lopata, A. L., Zinn, C., and Potter, P. C. (1997). Characteristics of hypersensitivity reactions and identification of a unique 49 Kd IgE-binding protein (Hal-m-1) in abalone (Haliotis... 

Fig. 2. Nacre of red abalone shell Halitotis refescens), imaged here by transmission electron microscopy (left), has a bricks-and-mortar structure. The bricks are CaCOs (aragonite) platelets, and the mortar is a composite of macromolecules, including structural proteins and polysaccharides, that form a thin film around the platelets. The three-dimensional structure is depicted on the right [23]...

Baxter, G. and Morse, D. E., Cilia from abalone larvae contain a receptor-dependent G protein transduction system similar to that in mammals, Biol. Bull., 183, 147, 1992. 

Among species which do have commercial value, the abalone, Haliotis gigantea, contains 23% protein, the wreath-shell. Turbo cornutus, 19% (Simidu et al., 1953). Both these species were from Japanese waters. 

Figure 4. Scheme showing sperm-egg interaction in the abalone. 1. The sperm binds to the egg VE by the plasma membrane at the tip of the AV (AG), (F, flagellum M, mitochondrion N, nucleus). 2. The sperm acrosome reacts releasing lysin and the 18K protein from its anterior tip. 3. Lysin disrupts the fibers of the VE and the 18K coats the extending acrosome process as it extends. 4. The sperm passes through the hole in the VE and the membrane covering the tip of the acrosomal process fuses with the egg (from Vacquier and Lee, 1993). 

The abalone sperm AR can be artificially induced by raising the calcium ion concentration of seawater from the normal 10 mM to 50 mM in seawater buffered with 10 mM Tris at pH 8.2. Unlike other species used for fertilization studies, the abalone AR does not lead to the rapid death of the sperm. In abalone sperm, the acrosomal compartment is sealed off from the respiratory compartment acrosome-reacted, sperm will continue to swim for days if stored in the cold room at 4°C. The acrosomal exudate of these sperm is composed predominantly of soluble ly sin and 18K protein. Reducing and denaturing polyacrylamide gel electrophoresis of whole sperm, AV exudate, and purified lysin shows that abalone spermatocytes make a substantial investment in the synthesis of these two acrosomal proteins (Figure 6). 

Figure 6. Polyacrylamide gel electrophoresis of abalone sperm and AV contents. Lanes A and E are standard proteins of known molecular mass. Lane B, whole sperm dissolved in SDS. Lane C, the acrosome vesicle content released to seawater when exocytosis of the sperm is induced by high calcium ion concentration. Lane D, purified 16-kDa lysin. (from Lewis et al., 1982).

Figure 8. The fusion of artificial phospholipid vesicles induced by 18K protein (a) and lysin (b) at the three concentrations indicated above (c, buffer alone). The upper panels are with sperm proteins from the red abalone (Hr H. refescens) the lower panels are with sperm proteins from the green abalone (Hf H. fulgens). The 18K proteins are more potent fusagens than lysin. Although the two 18K proteins are only 33.8% identical in primary structure, their five predicted amphipathic helices have similar hydrophobic moments (from Swanson and Vacquier, 1995a).

Figure 9. The alignments of lysin and the 18K proteins from five abalone species. Dots denote identity to the top sequence and dashes are inserted for alignment. Asterisks denote positions of perfect identity. In lysin,-18 to-1 is the signal sequence in18Kitis -17 to-1. The lengths of the mature proteins are given at the C-terminal ends. H. assimilis (threaded abalone) is closely related to H. kamtschatkana (pinto abalone). H. sorenseni is the white abalone (from Vacquier et al., 1997).

Primers were made to obtain the full length sequences of five species by PCR (Swanson and Vacquier, 1995b). Instead of presenting an alignment of all 27 lysin sequences and the five 18K sequences, we will present the sequences of both proteins from five species of California abalone (Figure 9 Vacquier et al., 1997). The sequences of both acrosomal proteins are known for four species. Haliotis kamtschatkana (known for lysin) and H. assimilis (known for 18K) are considered to be comparable, closely related species. 

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