The unique set of putative membrane-associated anti-sigma factors in Clostridium thermocellum suggests a novel extracellular carbohydrate-sensing mechanism involved in gene regulation.

FEMS Microbiol Lett 2010 Jul 23;308(1):84-93. Epub 2010 Apr 23.

Department of Molecular Microbiology and Biotechnology, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.

Genome analysis of the Gram-positive cellulolytic bacterium Clostridium thermocellum revealed the presence of multiple negative regulators of alternative sigma factors. Nine of the deduced proteins share a strong similarity in their N-terminal sequences to the Bacillus subtilis membrane-associated anti-sigma(I) factor RsgI and have an unusual domain organization. In six RsgI-like proteins, the C-terminal sequences contain predicted carbohydrate-binding modules. Three of these modules were overexpressed and shown to bind specifically to cellulose and/or pectin. Bioinformatic analysis of >1200 bacterial genomes revealed that the C. thermocellum RsgI-like proteins are unique to this species and are not present in other cellulolytic clostridial species (e.g. Clostridium cellulolyticum and Clostridium papyrosolvens). Eight of the nine genes encoding putative C. thermocellum RsgI-like anti-sigma factors form predicted bicistronic operons, in which the first gene encodes a putative alternative sigma factor, similar to B. subtilissigma(I), but lacking in one of its domains. These observations suggest a novel carbohydrate-sensing mechanism in C. thermocellum, whereby the presence of polysaccharide biomass components is detected extracellularly and the signal is transmitted intracellularly, resulting in the disruption of the interaction between RsgI-like proteins and sigma(I)-like factors, the latter of which serve to activate appropriate genes encoding proteins involved in cellulose utilization.

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http://dx.doi.org/10.1111/j.1574-6968.2010.01997.xDOI Listing
July 2010
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References

(Supplied by CrossRef)
Gapped BLAST and PSI-BLAST
Altschul et al.
a new generation of protein database search programs 1997

Bayer et al.
1996
Cellulosomes-structure and ultrastructure
Bayer et al.
J Struct Biol 1998
The cellulosomes
Bayer et al.
Multi-enzyme machines for degradation of plant cell wall polysaccharides 2004
Improved prediction of signal peptides
Bendtsen et al.
SignalP 3.0 2004
The Carbohydrate-Active EnZymes database (CAZy)
Cantarel et al.
an expert resource for Glycogenomics 2008
The Pfam protein families database
Finn et al.
Nucleic Acids Res 2010

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