Calvete J J, Carrera E, Sanz L, Töpfer-Petersen E
Institut für Reproduktionsmedizin, Tierärztliche Hochschule Hannover, Germany.
Biol Chem. 1996 Jul-Aug;377(7-8):521-7. doi: 10.1515/bchm3.1996.377.7-8.521.
AQN-1 and AQN-3 form part of the complement of surface-associated lectins which coat the plasma membrane overlying the acrosomal cap of in vitro capacitated boar spermatozoa. They belong to the spermadhesin protein family and have binding affinity for glycoconjugates of the zona pellucida, the extracellular investment surrounding mammalian eggs. The oligosaccharide and zona pellucida binding characteristics of spermadhesins AQN-1 and AQN-3 were investigated using a solid-phase assay and biotinylated glycoprotein ligands. Both sperm proteins bind glycoproteins containing Gal beta (1-4)-GlcNAc and Gal beta-(1-3)-GalNAc oligosaccharide sequences with dissociation constants (Kd) of 0.08 to 0.8 microM, and to zona pellucida glycoproteins with Kd = 0.15-0.25 microM. However, 5-N-acetyl neuraminic acid alpha (2-3/6)-linked to the galactose residue decreases the affinity of glycosylated ligands to AQN-1 three-fold, although it did not affect oligosaccharide binding to AQN-3. In addition, AQN-3 binds preferentially to glycoproteins with either a linear or tri- and tetraantennary carbohydrates than to those containing diantennary N-acetyllactosamine structures. The similar but distinct oligosaccharide recognition capabilities of spermadhesins AQN-1 and AQN-3 (this work) and AWN-1 (Dostálová, Z, Calvete, J.J., Sanz, L., and Töpfer-Petersen, E. (1995) Eur. J. Biochem. 230, 329-336) suggest that, in the pig, sperm-zona pellucida binding might be mediated by lectins displaying similar although distinct carbohydrate-recognition abilities.
AQN - 1和AQN - 3是表面相关凝集素复合物的一部分，这些凝集素覆盖在体外获能的公猪精子顶体帽上方的质膜上。它们属于精子黏附素蛋白家族，对透明带的糖缀合物具有结合亲和力，透明带是围绕哺乳动物卵子的细胞外结构。使用固相测定法和生物素化糖蛋白配体研究了精子黏附素AQN - 1和AQN - 3的寡糖及透明带结合特性。两种精子蛋白均与含有Galβ(1 - 4)-GlcNAc和Galβ-(1 - 3)-GalNAc寡糖序列的糖蛋白结合，解离常数（Kd）为0.08至0.8微摩尔，并且与透明带糖蛋白结合，Kd = 0.15 - 0.25微摩尔。然而，与半乳糖残基相连的5 - N - 乙酰神经氨酸α(2 - 3/6)使糖基化配体与AQN - 1的亲和力降低了三倍，尽管它不影响寡糖与AQN - 3的结合。此外，与含有双天线N - 乙酰乳糖胺结构的糖蛋白相比，AQN - 3优先结合具有线性或三天线和四天线碳水化合物的糖蛋白。精子黏附素AQN - 1和AQN - 3（本研究）以及AWN - 1（多斯塔洛娃，Z，卡尔维特，J.J.，桑斯，L.，和托普费尔 - 彼得森，E.（1995年）欧洲生物化学杂志230，329 - 336）相似但不同的寡糖识别能力表明，在猪中，精子与透明带的结合可能由具有相似但不同碳水化合物识别能力的凝集素介导。
