Figure 7. A model for regulation of the stoichiometry of cellulosomal components in vivo.

The cip-cel operon is transcribed by its sole promoter and the primary transcript is cleaved into several secondary transcripts by endonucleases as defined by iPSs. However, stability of these secondary transcripts against exonuclease degradation varied due to their distinct terminal structure. The resulted distinction in transcript level among the genes result in the observation of a ‘complex' type operon and eventually lead to the proper composition and ratio of cellulosome subunits in C. cellulolyticum.