Abstract
Expression of recombinant proteins fused to a novel glycomodule tag, termed hydroxyproline (Hyp)-O-glycosylated peptides (HypGP), was earlier found to boost secreted protein yields up to 500-fold in plant cell culture. Here, this technology was applied to the expression of human protease inhibitor α1-antitrypsin (AAT) in tobacco BY-2 cell culture. A designer HypGP tag composed of a 'Ala-Pro' motif of 20 units, or (AP)(20), was engineered either at the N- or C-terminal end of AAT. The (AP)(20) tag substantially increased the secreted yields of the recombinant AAT up to 34.7 mg/L. However, the (AP)(20)-tagged AAT products were frequently subjected to proteolytic processing. The intact AAT-(AP)(20) along with some of the truncated AAT domains exhibited desired biological activity in inhibiting elastase. The results from this research demonstrated that the designer (AP)(20) module engineered in BY-2 cells could function as a molecular carrier to substantially enhance the secreted yields of the recombinant AAT.