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首页> 外文期刊>Biochemistry >Difference in the binding mode of two mannose-binding proteins: demonstration of a selective minicluster effect.
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Difference in the binding mode of two mannose-binding proteins: demonstration of a selective minicluster effect.

机译：两种甘露糖结合蛋白结合模式的差异：选择性小团簇效应的证明。

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摘要

Serum-type and liver-type mannose-binding proteins (MBP) are both present in higher animals and both are composed of a carbohydrate-recognition domain (CRD) and a collagenous domain. Although known as mannose-binding proteins, these proteins bind N-acetylglucosamine and other related sugars quite well. An earlier specificity study using cloned CRD portions of both types of MBP from rat [Childs, R. A., Feizi, T., Yuen, C.-T., Drickamer, K., & Quesenberry, M. (1990) J. Biol. Chem. 265, 20770-20777] revealed that the liver MBP CRD binds the trimannosyl core structure of N-glycosides, whereas the serum MBP CRD does not. We studied the substrate preferences of these CRDs using both solid and solution phase assays, testing monosaccharides, glycoproteins, and synthetic cluster ligands. While there was no significant difference in the monosaccharide binding specificities of the two CRDs, they displayed very different affinities for natural glycoproteins and mannose-containing cluster glycosides. Most interestingly, synthetic cluster ligands with two terminal GlcNAc moieties have affinity equal to monovalent GlcNAc ligands toward both CRDs, whereas a series of structurally similar Man-terminated divalent ligand displays about 20-fold enhanced affinity toward liver CRD only. A plausible explanation is that the liver MBP CRD has two sugar binding sites per subunit, one of which binds only mannose, and the other, both mannose and N-acetylglucosamine. In contrast, the serum MBP CRD has only one site of the latter type. Results of isothermal titration calorimetry support this hypothesis.
机译：血清型和肝型甘露糖结合蛋白（MBP）都存在于高等动物中，并且都由碳水化合物识别域（CRD）和胶原域组成。尽管被称为甘露糖结合蛋白，但这些蛋白与N-乙酰氨基葡萄糖和其他相关糖的结合非常好。较早的特异性研究使用了来自大鼠的两种类型的MBP的克隆CRD部分[Childs，R.A.，Feizi，T.，Yuen，C.-T.，Drickamer，K.，＆Quesenberry，M.（1990）J.化学265，20770-20777]揭示肝脏MBP CRD结合N-糖苷的三甘露糖核心结构，而血清MBP CRD不结合。我们使用固相和溶液相分析，测试单糖，糖蛋白和合成簇配体研究了这些CRD的底物偏好。虽然两种CRD的单糖结合特异性没有显着差异，但它们对天然糖蛋白和含甘露糖的簇状糖苷显示出非常不同的亲和力。最有趣的是，具有两个末端GlcNAc部分的合成簇配体对两个CRD的亲和力均等同于单价GlcNAc配体，而一系列结构相似的曼末端二价配体对肝CRD的亲和力却提高了约20倍。一个合理的解释是肝脏MBP CRD每个亚基有两个糖结合位点，其中一个仅结合甘露糖，另一个结合甘露糖和N-乙酰氨基葡萄糖。相反，血清MBP CRD仅具有后者的一个位点。等温滴定量热法的结果支持该假设。

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