Structural modelling and thermostability of a serine protease inhibitor belonging to the Kunitz-BPTI family from the Rhipicephalus microplus tick

rBmTI-A is a recombinant serine protease inhibitor that belongs to the Kunitz-BPTI family and that was cloned from Rhipicephalus microplus tick. rBmTI-A has inhibitory activities on bovine trypsin, human plasma kallikrein, human neutrophil elastase and plasmin with dissociation constants in nM range. It is characterized by two inhibitory domains and each domain presents six cysteines that form three disulfide bonds, which contribute to the high stability of its structure. Previous studies suggest that serine protease inhibitor rBmTI-A has a protective potential against pulmonary emphysema in mice and anti-inflammatory potential. Besides that, rBmTI-A presented a potent inhibitory activity against in vitro vessel formation. In this study, the tertiary structure of rBmTI-A was modeled. The structure stabilization was evaluated by molecular dynamics analysis. Circular dichroism spectroscopy data corroborated the secondary structure found by the homology modelling. Also, in circular dichroism data it was shown a thermostability of rBmTI-A until approximately 70 degrees C, corroborated by inhibitory assays toward trypsin. (C) 2020 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.

Automated summary

rBmTI-A is a recombinant serine protease inhibitor belonging to the Kunitz-BPTI family, showing inhibitory activities against bovine trypsin, human plasma kallikrein, human neutrophil elastase, and plasmin. It has two inhibitory domains with six cysteines each, forming three disulfide bonds for high structural stability. Experimental results suggest its protective potential against pulmonary emphysema, anti-inflammatory properties, and potent inhibitory activity on in vitro vessel formation, while circular dichroism data confirmed its thermostability and secondary structure.