Abstract

Crystallographic and solution studies of Mevo lectin and its complexes, the first effort of its kind on an archeal lectin, reveal a structure similar to β-prism I fold lectins from plant and animal sources, but with a quaternary association involving a ring structure with seven-fold symmetry. Each subunit in the heptamer carries one sugar binding site on the first Greek key motif. The oligomeric interface is primarily made up of a parallel β-sheet involving a strand of Greek key I of one subunit and Greek key ΙΙΙ from a neighboring subunit. The crystal structures of the complexes of the lectin with mannose, αMan(1,2)αMan, αMan(1,3)αMan, a mannotriose and a mannopentose revealed a primary binding site similar to that found in other mannose specific β-prism I fold lectins. The complex with αMan(1,3)αMan provides an interesting case in which a few subunits have the reducing end at the primary binding site, while the majority have the nonreducing end at the primary binding site. The structures of complexes involving the trisaccharide and the pentasaccharide exhibit cross-linking among heptameric molecules. The observed arrangements may be relevant to the multivalency of the lectin. Phylogenetic analysis of amino acid sequences indicates that Mevo lectin is closer to β-prism I fold animal lectins than with those of plant origin. The results presented here reinforce the conclusion regarding the existence of lectins in all three domains of life. It would also appear that lectins evolved to the present form before the three domains diverged.

中文翻译：

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Mevo 凝集素的结构和相关研究来自 Methanococcus voltae A3：古细菌凝集素及其相互作用的首次全面表征

摘要

Mevo的晶体学和溶液研究凝集素及其复合物是对古菌凝集素的首次尝​​试，揭示了一种类似于 β-棱镜的结构 I 折叠植物和动物来源的凝集素，但具有涉及具有七重对称性的环状结构的四元关联。七聚体中的每个亚基在第一个希腊键基序上带有一个糖结合位点。寡聚界面主要由平行β-折叠组成，该β-折叠涉及一个亚基的希腊键I链和来自相邻亚基的希腊键III。凝集素与甘露糖、αMan(1,2)αMan、αMan(1,3)αMan、甘露三糖和甘露戊糖的复合物的晶体结构揭示了与其他甘露糖特异性 β-棱镜 I 中发现的相似的主要结合位点折叠凝集素。αMan(1, 3)αMan 提供了一个有趣的案例，其中少数亚基在初级结合位点具有还原端，而大多数亚基在初级结合位点具有非还原端。涉及三糖和五糖的复合物的结构表现出七聚体分子之间的交联。观察到的排列可能与凝集素的多价有关。氨基酸序列的系统发育分析表明与植物来源的凝集素相比，Mevo凝集素更接近于 β-prism I 折叠动物凝集素。这里提出的结果强化了关于在生命的所有三个领域都存在凝集素的结论。看起来凝集素在三个结构域分歧之前就进化成现在的形式。