| Structural highlights
Function
RSGI1_ACET2 Anti-sigma factor for SigI1. Negatively regulates SigI1 activity through direct interaction (PubMed:20937888). Binding of the polysaccharide substrate to the extracellular C-terminal sensing domain of RsgI1 may induce a conformational change in its N-terminal cytoplasmic region, leading to the release and activation of SigI1 (Probable).[1] [2]
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[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Nataf Y, Bahari L, Kahel-Raifer H, Borovok I, Lamed R, Bayer EA, Sonenshein AL, Shoham Y. Clostridium thermocellum cellulosomal genes are regulated by extracytoplasmic polysaccharides via alternative sigma factors. Proc Natl Acad Sci U S A. 2010 Oct 26;107(43):18646-51. doi:, 10.1073/pnas.1012175107. Epub 2010 Oct 11. PMID:20937888 doi:http://dx.doi.org/10.1073/pnas.1012175107
- ↑ Nataf Y, Bahari L, Kahel-Raifer H, Borovok I, Lamed R, Bayer EA, Sonenshein AL, Shoham Y. Clostridium thermocellum cellulosomal genes are regulated by extracytoplasmic polysaccharides via alternative sigma factors. Proc Natl Acad Sci U S A. 2010 Oct 26;107(43):18646-51. doi:, 10.1073/pnas.1012175107. Epub 2010 Oct 11. PMID:20937888 doi:http://dx.doi.org/10.1073/pnas.1012175107
- ↑ Yaniv O, Fichman G, Borovok I, Shoham Y, Bayer EA, Lamed R, Shimon LJ, Frolow F. Fine-structural variance of family 3 carbohydrate-binding modules as extracellular biomass-sensing components of Clostridium thermocellum anti-sigma(I) factors. Acta Crystallogr D Biol Crystallogr. 2014 Feb;70(Pt 2):522-34. doi:, 10.1107/S139900471302926X. Epub 2014 Jan 31. PMID:24531486 doi:http://dx.doi.org/10.1107/S139900471302926X
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