Vacquier V D, Carner K R, Stout C D
Scripps Institution of Oceanography, University of California, San Diego, La Jolla 92093.
Proc Natl Acad Sci U S A. 1990 Aug;87(15):5792-6. doi: 10.1073/pnas.87.15.5792.
Abalone eggs are contained within a rigid, elevated vitelline envelope through which the sperm must pass before reaching the egg cell membrane. Abalone spermatozoa possess an acrosomal protein called lysin that creates a hole in the egg vitelline envelope by a nonenzymatic mechanism. Lysins from two species of abalone, termed pink and red, which share the same habitat, exhibit species specificity in the dissolution of isolated egg envelopes. Cloning and sequencing the cDNAs for pink and red abalone lysins reveal transcript lengths of approximately 660 nucleotides. The open reading frames of 465 (pink) and 462 (red) nucleotides show a 13% difference. The 3' untranslated regions before the poly(A) tails are 170 (pink) and 165 (red) nucleotides long and differ from each other by about 7%. The protein sequences show nearly identical signal sequences of 18 amino acids for both lysins. The mature protein is 137 amino acids in the pink abalone and 136 in the red abalone; the two mature lysins differ in 29 of 137 amino acids (21%). The most variable region, which may account for lysin's species specificity, is at the NH2 terminus, where 11 of the 15 amino acids differ between the two species. Predictions of secondary structure indicate that both lysins contain four homologous amphiphilic alpha-helices.
鲍鱼卵被包裹在一个坚硬、隆起的卵黄膜内，精子在到达卵细胞表面之前必须穿过该膜。鲍鱼精子含有一种名为溶解素的顶体蛋白，它通过非酶机制在卵黄膜上形成一个孔。来自两种同域分布的鲍鱼（分别称为粉鲍和红鲍）的溶解素，在溶解分离出的卵膜时表现出物种特异性。对粉鲍和红鲍溶解素的cDNA进行克隆和测序后发现，转录本长度约为660个核苷酸。465个核苷酸（粉鲍）和462个核苷酸（红鲍）的开放阅读框显示出13%的差异。在poly(A)尾之前的3'非翻译区，粉鲍为170个核苷酸，红鲍为165个核苷酸，彼此相差约7%。两种溶解素的蛋白质序列显示出几乎相同的18个氨基酸的信号序列。成熟蛋白在粉鲍中为137个氨基酸，在红鲍中为136个氨基酸；两种成熟溶解素在137个氨基酸中有29个不同（21%）。最具变异性的区域可能是溶解素物种特异性的原因，位于NH2末端，两种物种在该区域的15个氨基酸中有11个不同。二级结构预测表明，两种溶解素都含有四个同源的两亲性α螺旋。
