Computational design, functional analysis and antigenic epitope estimation of a novel hybrid of 12 peptides of hirudin and reteplase.

Cardiovascular and cerebrovascular diseases are leading causes of morbidity and mortality for human beings, and thrombosis is the major risk factor. Thrombolytic therapy has been testified to be the most effective approach to cure thrombosis-related diseases. In clinical treatment, we often adopt a combination therapeutic regimen of both thrombolytic and anticoagulant agents to prevent the recurrence of thrombosis. Thus, a novel hybrid (HV12p-rPA) comprised of the C-terminal 12 residues of hirudin-PA (HV12p) and reteplase (rPA) was designed. The three-dimensional structure of this hybrid was mimicked based on homology modeling and refined with dynamics simulation by utilizing Amber12.0 software. The function of the hybrid was analyzed by structure comparison and the root mean square deviation (RMSD) of Cα atoms between the hybrid and native rPA was calculated. The results showed that HV12p, which was located in the N-terminus of the hybrid, was far from the rPA segment of the hybrid and had no influence on the conformational stability of the rPA domain. The RMSD of Cα atoms of these superimposed proteins was about 40Å, implying that the hybrid had a similar spatial conformation to that of native rPA. Additionally, the antigenic epitopes of the hybrid were predicted by estimations of Hopp-Wood hydrophilicity, Janin accessibility, Zimmermane-Simha polarity, Bhaskaran-Ponnuswamy flexibility, as well as secondary structure analysis and Kolaskar-Tongaonkar antigenicity prediction. The results showed that the most likely antigenic determinants were located at or near regions 148-152, 257-262 and 321-330.