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首页> 外文期刊>Biochemistry >ABA-1 ALLERGEN OF THE PARASITIC NEMATODE ASCARIS SUUM - FATTY ACID AND RETINOID BINDING FUNCTION AND STRUCTURAL CHARACTERIZATION
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ABA-1 ALLERGEN OF THE PARASITIC NEMATODE ASCARIS SUUM - FATTY ACID AND RETINOID BINDING FUNCTION AND STRUCTURAL CHARACTERIZATION

机译：寄生线虫天牛脂肪酸和维甲酸的ABA-1过敏原结合功能及其结构表征。

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We report here on the structure and function of the ABA-1 allergen protein of the parasitic nematode Ascaris, the first nematode allergen to be characterized in detail, Using the fluorescent fatty acid analog 11-(((5-(dimethylamino)-1-naphthalenyl)sulfonyl)amino)undecanoic acid (DAUDA), it was demonstrated that ABA-1 is a fatty acid binding protein (FABP) with a high affinity for the fluorescent analog (8.8 x 10(-8) M) and for oleic acid in competition experiments (1.3 x 10(-8) M), with a single binding site for ligand per monomer unit, Blue-shifting of fluorescence emission of DAUDA upon binding was unprecedented in degree among FABPs, being equivalent to that occurring in cyclohexane. A similarly blue-shifted spectrum was obtained with a probe in which the fluorophore was bound to the alpha carbon of a fatty acid, indicating that the carboxylate group of bound fatty acids is probably not exposed to solvent. In competition experiments and by observation of changes in their intrinsic fluorescence, retinol and retinoic acid were also found to bind in the fatty acid binding site. Circular dichroism (CD) of the ABA-1 protein revealed a high alpha-helix content (59%) which was consistent with the four-helix structure for the protein predicted from sequence algorithms. Fluorescence measurements showed that the single, highly conserved tryptophan residue is deeply buried in an unusually apolar environment and that this was unaffected by ligand binding. DSC studies of thermal stability indicate that unfolding of the ABA-1 dimer is cooperative and biphasic (T-m approximate to 71 and 89 degrees C), suggesting a two-domain thermal unfolding process, again consistent with the predicted structure. Only the folding of the high-temperature domain is reversible on cooling. DSC confirmed the gel filtration analysis, which indicated that ABA-1 forms a dimer. Aside from being the first nematode allergen for which structure or function has been elucidated, ABA-1 provides a highly manipulable model for investigation of the interaction between hydrophobic ligands and alpha-helical proteins.
机译：我们在这里报告寄生线虫A虫的ABA-1过敏原蛋白的结构和功能，这是第一个被详细表征的线虫过敏原，使用荧光脂肪酸类似物11-（（（5-（二甲基氨基）-1-萘基），磺酰基）氨基）十一酸（DAUDA），证明ABA-1是一种脂肪酸结合蛋白（FABP），对荧光类似物（8.8 x 10（-8）M）和油酸具有很高的亲和力在竞争实验（1.3 x 10（-8）M）中，每个单体单元都有一个配体结合位点，结合后DAUDA荧光发射的蓝移在FABP中的程度是空前的，与环己烷中发生的程度相同。用探针获得了类似的蓝移光谱，在该探针中，荧光团与脂肪酸的α碳键合，表明所结合的脂肪酸的羧酸酯基可能​​未暴露于溶剂中。在竞争实验中，通过观察其固有荧光的变化，还发现视黄醇和视黄酸在脂肪酸结合位点结合。 ABA-1蛋白的圆二色性（CD）显示出高的α-螺旋含量（59％），这与根据序列算法预测的蛋白的四螺旋结构一致。荧光测量表明，单个高度保守的色氨酸残基深深地埋在异常的非极性环境中，并且不受配体结合的影响。 DSC对热稳定性的研究表明，ABA-1二聚体的展开是协同的和双相的（T-m约为71和89摄氏度），表明存在一个两域热展开过程，再次与预测的结构一致。冷却时仅高温区域的折叠是可逆的。 DSC证实了凝胶过滤分析，表明ABA-1形成二聚体。除了是第一个阐明了结构或功能的线虫变应原外，ABA-1还提供了高度可操作的模型来研究疏水性配体与α螺旋蛋白之间的相互作用。

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