Cellulose synthase activation domains

Figure 11-1. The cellulose synthase life cycle. After being inserted into the plasma membrane within a cellulose synthase activation domain (CSAD located between the red circles at the time of deposition) the synthase moves with an average speed w within the plasma membrane, leaving a cellulose microfibril in its wake. The direction of motion and hence the angle the deposited CMF mals s with the cell axis is determined by the local density of other synthases. The CMF synthase becomes inactive after a characteristic lifetime which determines the length of the microfibrils The CSAD itself, here shown in grey, moves with a speed v in the direction opposite to that of the CMF synthases (See Color Plate of this figure beginning on page 355)...

In the cellulose-producing bacterium Acetobacter xylinum, the phosphodiesterase A1 protein (AxPDEAl) functions to hydrolyze a potent allosteric activator of the bacterial cellulose synthase, the cyclic nucleotide [cyclic bis(3 —> 5 )diguanylic acid, or c-di-GMP] (17). xPDEAl was recently shown to contain an N-terminal regulatory heme-PAS domain that, when bound to O2, inhibits the C-terminal phosphodiesterase activity (10). Thus in cultures of this obligate aerobe, O2 is now thought to enhance the construction of a buoyant cellulose pellicle by the cells nearest to the media surface for possible use as a biofilm. The type of phosphodiesterase domain found in AxPDEAl, though not extensively studied, is widespread in Bacteria. 

---