Fine-structural variance of family 3 carbohydrate-binding modules as extracellular biomass-sensing components of Clostridium thermocellum anti-σI factors.
Fine-structural variance of family 3 carbohydrate-binding modules as extracellular biomass-sensing components of Clostridium thermocellum anti-σI factors.
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DOI：
10.1107/s139900471302926x
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发表时间：
2014-02
期刊：
影响因子：
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通讯作者：
Oren Yaniv;Galit Fichman;I. Borovok;Y. Shoham;E. Bayer;R. Lamed;L. Shimon;F. Frolow
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文献类型：
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作者：
Oren Yaniv;Galit Fichman;I. Borovok;Y. Shoham;E. Bayer;R. Lamed;L. Shimon;F. Frolow
厌氧、嗜热、产生纤维素酶体的细菌热纤梭菌（Clostridium thermocellum）依赖于多种碳水化合物活性酶，以便有效地将复杂碳水化合物分解成可利用的单糖。直到最近，基因组分析揭示了一组假定的操纵子，才知道了纤维素体基因的调控机制。在一些实施方案中，所述热纤蛋白包含编码σI因子（即控制特化调节子活化的替代σ因子）和它们的同源抗σI因子（RsgI）的热纤蛋白。这些推定的抗σ I因子蛋白具有被认为是碳水化合物传感器的模块。其中三个模块被结晶，并解决了它们的三维结构。结构显示出与纤维素体家族3碳水化合物结合模块（CBM 3）的高度整体序列和结构相似性。的三个碳水化合物传感器（RsgI-CBM 3）和参考CBM 3的结构进行了比较的上下文中的纤维素和复合碳水化合物结合的特异性的结构决定因素。RsgI-CBM 3之间的精细结构变化似乎导致每个传感器的替代衬底偏好。
The anaerobic, thermophilic, cellulosome-producing bacterium Clostridium thermocellum relies on a variety of carbohydrate-active enzymes in order to efficiently break down complex carbohydrates into utilizable simple sugars. The regulation mechanism of the cellulosomal genes was unknown until recently, when genomic analysis revealed a set of putative operons in C. thermocellum that encode σI factors (i.e. alternative σ factors that control specialized regulon activation) and their cognate anti-σI factor (RsgI). These putative anti-σI-factor proteins have modules that are believed to be carbohydrate sensors. Three of these modules were crystallized and their three-dimensional structures were solved. The structures show a high overall degree of sequence and structural similarity to the cellulosomal family 3 carbohydrate-binding modules (CBM3s). The structures of the three carbohydrate sensors (RsgI-CBM3s) and a reference CBM3 are compared in the context of the structural determinants for the specificity of cellulose and complex carbohydrate binding. Fine structural variations among the RsgI-CBM3s appear to result in alternative substrate preferences for each of the sensors.