Signal molecules in the jelly coat of starfish eggs for the inducing of acrosome reaction.

顶体反应(AR)是精子对卵子包膜的一种特定的胞吐反应。在海星Asterias amurensis中，卵子凝胶层中的三种成分协同作用于精子，引发AR，即顶体反应诱导物质(ARIS)、Co-ARIS和称为Asterosap的精子激活肽。ARIS是一种高度硫酸盐化的糖蛋白，其表观分子尺寸超过10^7，其活性主要归因于硫酸盐化糖链。ARIS的主要糖链是一个很长的(分子尺寸为2×10~(-6))的五糖重复单元(Fr.1)线性聚合物，能够在高钙浓度下诱导AR，与ARIS一样。为了获得ARIS受体的结合参数，使用放射性标记的Fr.1进行了结合实验。精子与放射性碘标记的Fr.1孵育。根据Scatchard图，有两种类型的受体，即高亲和型(Kd；145um，Bmax；8.38×10^4)和低亲和型(Kd；4.43×10^2，Bmax；1.89×10^6)。并与未标记的Fr.1和标记的Fr.1进行竞争试验。测定了配体的结合浓度和游离态浓度。结果表明，非标记的Fr.1对标记的Fr.1的结合有抑制作用。

The acrosome reaction (AR) is a species-specific exocytosis response of spermatozoa to the egg envelopment. In the starfish Asterias amurensis, three components in the jelly coat of eggs act in concert on spermatozoa to elicit the AR ; namely acrosome reaction-inducing substance (ARIS), Co-ARISs and sperm-activating peptides named asterosaps. ARIS is highly sulfated glycoprotein of an apparent molecular size over 10^7 and its activity is mostly attributable to sulfated sugar chains. The main saccharide chain of ARIS is a very long (2 x 10^6 in more in molecular size) linear polymer of the pentasaccharide repeating units (Fr.1) is able to induce the AR at high calcium concentration as well as ARIS does. To obtain binding parameters of an ARIS receptor, binding experiments were carried out by centrifugation binding assay using radio-labeled Fr.1. Spermatozoa were incubated with radioactive iodinated Fr.1. With Scatchard plot, there are two type receptor, High affinity type (Kd ; 145 muM,Bmax ; 8.38 x 10^4) and low affinity type (Kd ; 4.43 x 10^2muM,Bmax ; 1.89 x 10^6). And competitive assay were carried with non-labeled Fr.1 and ^<125>I labeled Fr.1. The bound and free concentration of the ligand were measured. The result showed that non-labeled Fr.1 inhibits to bind labeled Fr.1.