Insights into the 3-D structure of a Kunitz inhibitor isolated from Daboia russelii

A. Munawar, N. Tariq, A. I. Durrani, H. Ajaz, A. K. Durrani

Abstract


Kunitz Inhibitor (Q2ES47) is a Kunitz-type serine protease inhibitor isolated from the venom of the Daboia russelii (Russel's viper) (Vipera russelii). This molecule binds to and blocks the activity of a range of serine proteases, like trypsin. In the present work 3-D model of the Kunitz Inhibitor (Q2ES47) was prepared with the online software UniProtKB/Swiss-Prot. The polypeptide (Q2ES47) shows a similar overall fold as that of Aprotinin (PDB ID: 1BPI). The P1 residue in Aprotinin is lysine while in (Q2ES47) it is arginine. Arginine has a complex guanidinium group cap on its side chain in contrast to lysine, which has a simple amino group at the end of its side chain. The presence of arginine with a bulky group on its side chain may show more specific binding pattern towards the serine proteases and might serve as an alternate antibleeding agent, with fewer side effects than Aprotinin. In addition to this the polypeptide (Q2ES47) was also submitted to NCBI BLAST, in order to search for similar sequence peptides in other snake venom. The kunitz inhibitors having homology above 60 % were selected and aligned in Clustal Omega, to study regions of similarity and therefore predict conserved regions.


Keywords


Snake venom, Molecular model, Kunitz inhibitor, Daboia russelii

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