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

顶体反应（AR）是精子对卵包膜的一种特异性胞吐反应。在海星（Asterias amurensis）中，卵的果冻外壳中的三种成分共同作用于精子引起AR；即顶体反应诱导物质（ARIS）、co -ARIS和精子激活肽（asterosaps）。ARIS是一种高度硫酸糖蛋白，表观分子大小超过10^7，其活性主要归因于硫酸糖链。ARIS的主糖链是一个很长的（2 × 10^6的分子大小）五糖重复单元（fr1）的线性聚合物，能够在高钙浓度下诱导AR和ARIS一样。为了获得ARIS受体的结合参数，采用放射性标记Fr.1离心结合实验进行了结合实验。精子用放射性碘化Fr.1孵育。Scatchard图显示，受体分为高亲和型（Kd; 145 muM,Bmax; 8.38 x 10^4）和低亲和型（Kd; 4.43 x 10^2muM,Bmax; 1.89 x 10^6）。用未标记的fr1和^<125 bb0标记的fr1进行竞争试验。测定了配体的结合浓度和游离浓度。结果表明，未标记的Fr.1抑制与标记的Fr.1结合。

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.