Fine-structural variance of family 3 carbohydrate-binding modules as extracellular biomass-sensing components of Clostridium thermocellum anti-σI factors

Oren Yaniv, Galit Fichman, Ilya Borovok, Yuval Shoham, Edward A. Bayer, Raphael Lamed, Linda J.W. Shimon, Felix Frolow

Research output: Contribution to journalArticlepeer-review

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 languageEnglish
Pages (from-to)522-534
Number of pages13
JournalActa Crystallographica Section D: Biological Crystallography
Volume70
Issue number2
DOIs
StatePublished - Feb 2014

Keywords

  • Clostridium thermocellum
  • RsgI-CBM3
  • anti-σ factors
  • family 3 carbohydrate-binding modules

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