Abstract
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.
Original language | English |
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Pages (from-to) | 522-534 |
Number of pages | 13 |
Journal | Acta Crystallographica Section D: Biological Crystallography |
Volume | 70 |
Issue number | 2 |
DOIs | |
State | Published - Feb 2014 |
Externally published | Yes |
Keywords
- Clostridium thermocellum
- RsgI-CBM3
- anti-σ factors
- family 3 carbohydrate-binding modules