Alves A P, Mulloy B, Moy G W, Vacquier V D, Mourão P A
Departamento de Bioquímica, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Caixa Postal 68041, Rio de Janeiro, RJ, 21941-590, Brazil.
Glycobiology. 1998 Sep;8(9):939-46. doi: 10.1093/glycob/8.9.939.
The egg jelly coats of sea urchins contain sulfated fucans which bind to a sperm surface receptor glycoprotein to initiate the signal transduction events resulting in the sperm acrosome reaction. The acrosome reaction is an ion channel regulated exocytosis which is an obligatory event for sperm binding to, and fusion with, the egg. Approximately 90% of individual females of the sea urchin Strongylocentrotus purpuratus spawned eggs having only one of two possible sulfated fucan electrophoretic isotypes, a slow migrating (sulfated fucan I), or a fast migrating (sulfated fucan II) isotype. The remaining 10% of females spawned eggs having both sulfated fucan isotypes. The two sulfated fucan isotypes were purified from egg jelly coats and their structures determined by NMR spectroscopy and methylation analysis. Both sulfated fucans are linear polysaccharides composed of 1-->3-linked alpha-L-fucopyranosyl units. Sulfated fucan I is entirely sulfated at the O -2 position but with a heterogeneous sulfation pattern at O -4 position. Sulfated fucan II is composed of a regular repeating sequence of 3 residues, as follows: [3-alpha-L-Fuc p -2,4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-1-->3-alpha-L-Fuc p -4(OSO3)-1]n. Both purified sulfated fucans have approximately equal potency in inducing the sperm acrosome reaction. The significance of two structurally different sulfated fucans in the egg jelly coat of this species could relate to the finding that the sperm receptor protein which binds sulfated fucan contains two carbohydrate recognition modules of the C-type lectin variety which differ by 50% in their primary structure.
海胆的卵胶膜含有硫酸化岩藻聚糖，这些硫酸化岩藻聚糖与精子表面受体糖蛋白结合，引发信号转导事件，从而导致精子顶体反应。顶体反应是一种离子通道调节的胞吐作用，是精子与卵子结合并融合的必要事件。紫海胆（Strongylocentrotus purpuratus）约90%的个体所产的卵仅含有两种可能的硫酸化岩藻聚糖电泳同工型中的一种，即迁移缓慢的（硫酸化岩藻聚糖I）或迁移快速的（硫酸化岩藻聚糖II）同工型。其余10%的雌性所产的卵含有两种硫酸化岩藻聚糖同工型。从卵胶膜中纯化出这两种硫酸化岩藻聚糖同工型，并通过核磁共振光谱和甲基化分析确定其结构。两种硫酸化岩藻聚糖都是由1→3连接的α-L-岩藻糖吡喃糖单元组成的线性多糖。硫酸化岩藻聚糖I在O-2位置完全硫酸化，但在O-4位置具有不均匀的硫酸化模式。硫酸化岩藻聚糖II由3个残基的规则重复序列组成，如下：[3-α-L-岩藻糖基-2,4(OSO3)-1→3-α-L-岩藻糖基-4(OSO3)-1→3-α-L-岩藻糖基-4(OSO3)-1]n。两种纯化的硫酸化岩藻聚糖在诱导精子顶体反应方面具有大致相同的效力。该物种卵胶膜中两种结构不同的硫酸化岩藻聚糖的意义可能与以下发现有关：结合硫酸化岩藻聚糖的精子受体蛋白含有两个C型凝集素种类的碳水化合物识别模块，它们的一级结构相差50%。
