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Publication Abstract from PubMed

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 sigma(I) factors (i.e. alternative sigma factors that control specialized regulon activation) and their cognate anti-sigma(I) factor (RsgI). These putative anti-sigma(I)-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.

Fine-structural variance of family 3 carbohydrate-binding modules as extracellular biomass-sensing components of Clostridium thermocellum anti-sigma(I) factors.,Yaniv O, Fichman G, Borovok I, Shoham Y, Bayer EA, Lamed R, Shimon LJ, Frolow F Acta Crystallogr D Biol Crystallogr. 2014 Feb;70(Pt 2):522-34. doi:, 10.1107/S139900471302926X. Epub 2014 Jan 31. PMID:24531486^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.