Processing of cellulose synthase (AcsAB) from Gluconacetobacter hansenii 23769

The cellulose synthase protein (AcsAB) is encoded by a single gene in Gluconacetobacter hansenii ATCC 23769. We have examined the processing pattern of this enzyme and the localization of the cleavage products by heterologously expressing the truncated portions of the AcsAB protein and using specific antibodies generated against these regions. We found that the AcsAB protein is processed into three polypeptide subunits of molecular masses 46 kDa, 34 kDa and 95 kDa. The 46 kDa polypeptide (AcsAcat) harbors the conserved glycosyltransferase domain and hence contains the catalytic subunit of the enzyme. This polypeptide is localized in the cytoplasmic membrane. The 34 kDa polypeptide (AcsAreg) is the regulatory subunit with the cyclic diGMP-binding PilZ domain. This polypeptide is largely cytoplasmic. The 95 kDa subunit (AcsB) is of unknown function and contains a predicted signal peptide at its N-terminus. This subunit is localized in the outer membrane. In addition to this, we have also localized the AcsC protein in the outer membrane, confirming its predicted localization based on the OM-signal sequence at its N-terminus.