The anaerobic cellulolytic bacterium Clostridium clariflavum degrading cellulose with the help of cellulosom complex. The scaffoldin protein, which is the backbone protein of the cellulosome complex, has nine cohesin modules to mount dockerin-containing enzyme molecules onto the complex for efficient degradation of cellulosic mass. The bacterium can express over 70 different dockerin-containing enzymes that can degrade diverse types of cellulosic materials into simpler soluble polysaccharides that the bacterium can use as energy source, so how does it regulates the expression of those enzymes?
Some cellulolytic bacteria employs a transcription regulation system that involves alternative sigma - anti-sigma factors SigI-RsgI. The C-termini of the anti-sigma factors (RsgIs) usually comprise protein modules which bind various carbohydrate materials and act as specific biosensors of components of biomass. We assume that when the C-terminal module of an RsgI binds a specific type of carbohydrate, a signal is transferred through its trans-membrane domain and the cognate sigma factor, thereby enabling transcription.
C. clariflavum possesses three RsgI-CBM3b systems, which the C-terminal CBMs are characterized in this study. In our work we would try to clarify the differences that reflect the predicted functional diversity of those modules.
In addition, C. clariflavum possesses few fused SigI-RsgI systems, which have an E_set motif at their C-termini. In our work we try to characterize those E_set motifs by determining structure and function. In addition we would try exploring the mode of action of the fused SigI-RsgI systems.
