GlyR3, a LacI family carbon catabolite repressor in Clostridium thermocellum
Tuesday, April 29, 2014
Exhibit/Poster Hall, lower level (Hilton Clearwater Beach)
Jinlyung Choi, Chemical and Biomolecular Engneering, University of Tennessee, Knoxville, TN, Dawn Klingeman, BioEnergy Science Center, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, Steven D. Brown, Biosciences Division and BioEnergy Science Center, Oak Ridge National Laboratory, Oak Ridge, TN and Chris D. Cox, Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, TN
The celC operon consists of the genes celC, glyR3 and licA. The genes celC and licA encode for genes with the hydrolytic activity for plant cell walls, while GlyR3 is a LacI family protein that autorepresses the celC operon. Repression of the operon is relived in the presence of laminaribiose, a beta-1,3, glucose-dimer (Newcomb et al, Proc Natl Acad Sci U S A 104(10): 3747–3752, 2007)

LacI family proteins are often involved in regulation of carbon metabolism across many genes. For example, CcpA is a LacI family protein in Bacillus subtilis and major carbon catabolite repressor. There are at least 44 known regulation sites for CcpA in Bacillus subtilis.  We found that GlyR3 is similar in sequence to CcpA, and on this basis we used CcpA binding sequences to search for putative GlyR3 binding sites in C. thermocellum. We found a putative GlyR3 binding site embedded in the coding region of manB which encodes for mananase. Through in vitro transcription, in vivo gene expression, and electrophoretic mobility shift assays, we were able to infer the regulation mechanism of manB.   We will also report on the results of RNA-seq based comparison of gene expression with and without laminaribiose to further investigate genes regulated by GlyR3.