Transcriptional regulation of the Clostridium cellulolyticum "cip-cel" operon: a complex mechanism involving a catabolite-responsive element

Laboratoire de Bioénergétique et Ingénierie des Protéines -UPR 9036-CNRS and Université d'Aix-Marseille, France

^* To whom correspondence should be addressed. Email: tardif{at}ibsm.cnrs-mrs.fr.

	Abstract

The cip-cel cluster of genes plays an important role in the catabolism of cellulose substrate by Clostridium cellulolyticum. It encodes several key components of the cellulosomes, including the scaffolding protein CipC and the major cellulase Cel48F. All the genes of this cluster display linked transcription, focusing attention on the promoter upstream from the first gene, cipC. We analyzed the regulation of the cipC promoter, using a transcriptional fusion approach. A single promoter is located between nucleotides -671 and -643 with respect to the ATG start codon, and the large mRNA leader sequence is processed at position -194. A catabolite-responsive element (CRE) 414 nucleotides downstream from the transcriptional start site has been shown to be involved in regulating this operon by a carbon catabolite repression mechanism. This CRE is thought to bind a CcpA-like regulator complexed with a P-Ser-Crh–like protein. Sequences surrounding promoter sequence may also be involved in direct (sequence-dependent DNA curvature), or indirect (unknown regulator binding) regulation.