The design of a new truncated and engineered alpha1-antitrypsin based on theoretical studies: an antiprotease therapeutics for pulmonary diseases

Nazanin Pirooznia, Sadegh Hasannia, Seyed Shahriar Arab, Abbas Sahebghadam Lotfi, Mostafa Ghanei, Abbas Shali

Alpha 1- antitrypsin (alpha1AT) a 54 kDa glycoprotein is a protease inhibitor. In the absence of alpha1AT, elastase released by lung macrophages, was not inhibited and lead to elastin breakdown and pulmonary problems such as emphysema or COPD. alpha1AT has three site of N-glycosylation and a characteristic reactive central loop (RCL). As small-scale medicines are preferred for pulmonary drug delivery, in this study alpha1ATs (1, 2, 3, 4 and 5) were engineered and shortened from the N-terminal region. In order to investigate the effect of different mutations and the deletion of 46 amino acids theoretical studies were performed. Homology modeling was performed to generate the 3D structure of alpha1ATs. The 10 ns Molecular Dynamic (MD) simulations were carried out to refine the models. Results from MD and protein docking showed that alpha1AT2 has the highest binding affinity for neutrophil elastase, provided the basis for the experimental phase in which sequences from the five alpha1AT constructs were inserted into the expression vector pGAPZalpha and expressed in the yeast Pichia pastoris. Although, the alpha1AT2 construct has the highest inhibitory activity even more that the native construct (alpha1AT5), results indicated the presence of protease inhibitory function of all the proteins' construct against elastase.