High-avidity, low-affinity multivalent interactions and the block to polyspermy in Xenopus laevis
High-avidity, low-affinity multivalent interactions and the block to polyspermy in Xenopus laevis
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DOI：
10.1021/ja020536f
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发表时间：
2002-11-06
影响因子：
15
通讯作者：
Boons, GJ
中科院分区：
文献类型：
--
作者：
Arranz-Plaza, E;Tracy, AS;Boons, GJ
凝集素XL35与非洲爪蟾卵母细胞周围的果冻外壳蛋白（JCP）的相互作用是阻碍多精子形成的重要因素。这一事件的分子细节尚不清楚，本研究的目的是描述受精包膜的形成机制。合成了一系列jcp衍生的低聚糖，并将其安装在人工氨基丙基臂上。该臂允许通过氨基乙酰化制备单价衍生物或通过附着在活化的聚丙烯酰胺聚合物上合成多价化合物。许多分析技术，包括酶联凝集素测定和表面等离子体共振，已经被开发并用于研究单价和多价化合物与XL35的相互作用。结果表明，凝集素XL35对含半乳糖的糖类具有非常广泛的特异性，其亲和力仅受末端糖的端粒结构或分支糖的同源性和连锁模式等次要特征的轻微调节。当糖以多价方式呈现时，也观察到广泛的特异性。与相应的单价对应物相比，糖共聚物的价校正亲和力增加了10-20倍。虽然合成聚合物不如JCP有效，但它们相互作用的动力学与天然配体的动力学非常接近，并且在每种情况下都观察到极长时间的相互作用。本研究的结果表明，在X. laevis中，多价性的真正生物学功能不是在XL35与其天然配体之间建立一个极其紧密的结合复合物，而是建立一个非常稳定的保护层，它不会解离，而且足够灵活，可以包裹发育中的胚胎。据推测，即使这些伙伴不能在生物事件的时间尺度上达到真正的平衡，它们的相互作用模式仍然可以保证对多精现象存在不可逾越的物理障碍。这项研究还强调，多价相互作用需要很长时间才能达到平衡，这一特征很可能是文献中报道的多价配体评估时的一些模糊性的起源。
The interaction of the lectin XL35 with the jelly coat protein (JCP) surrounding oocytes in Xenopus laevis is essential for the block to polyspermy. The molecular details of this event are poorly understood, and the present study has been undertaken with a view to delineating the mechanism of formation of the fertilization envelope. A range of JCP-derived oligosaccharides were synthesized, and all were installed with an artificial aminopropyl arm. This arm allowed the preparation of monovalent derivatives by acetylation of the amino group or the synthesis of polyvalent compounds by attachment to an activated polyacrylamide polymer. A number of analytical techniques, including enzyme-linked lectin assays and surface plasmon resonance, have been developed and utilized to study the interactions of the mono- and polyvalent compounds with XL35. The results reveal that the lectin XL35 has remarkably broad specificity for galactose-containing saccharides and the affinities are only slightly modulated by secondary features, such as anomeric configuration of the terminal sugar or the identity and linkage pattern of branching sugars. Broad specificity was also observed when the saccharides were presented in a polyvalent fashion. The glycopolymers displayed 10-20-fold increases in valency-corrected affinities compared to the corresponding monovalent counterparts. Although the synthetic polymers are not as potent as the JCP, the kinetics of their interactions mirror closely those of the native ligand, and in each case extremely long-lived interactions were observed. The results of this study indicate that, in X. laevis, the true biological function of multivalency is not to create an extremely tightly binding complex between XL35 and its natural ligand but, instead, to create a very stable protective layer that will not dissociate and is yet flexible enough to encapsulate the developing embryo. It is postulated that, even if these partners are unable to attain true equilibrium on the time scale of the biological event, their mode of interaction would, nevertheless, be expected to guarantee an insurmountable physical block to polyspermy. This study has also highlighted that multivalent interactions require a very long time to achieve equilibrium, and this feature may well be the origin of several of the ambiguities reported in the literature when multivalent ligands have been evaluated.