Structural Findings and Molecular Modeling Approach of a TFPI-Like Inhibitor
Kerly Fernanda Mesquita Pasqualoto, Andrea Balan, Sandra Alves Barreto, Simone Michaela Simons and Ana Marisa Chudzinski-Tavassi
Affiliation: Laboratorio de Bioquimica e Biofisica, Instituto Butantan, Avenida Vital Brasil, 1500, Sao Paulo, SP 05503-900, Brasil.
Keywords: Amblyomin-X, circular dichroism, molecular modeling, molecular dynamics simulation, TFPI-like inhibitor.
Specific blood coagulation inhibitors from hematophagous organisms, with different structures and novel
mechanism of action, have been described and they represent promising agents for the treatment of a variety of human
diseases related to coagulation and cancer. In our lab, the salivary glands transcriptome of the adult Amblyomma cajennense
tick was previously characterized by expressed sequence tags (EST). A transcript that codes for a tissue factor
pathway inhibitor (TFPI)-like protein with unique structure was found, and the recombinant form of this protein was
named Amblyomin-X. This protein was able to inhibit the factor Xa amidolytic activity and the activation of factor X by
the extrinsic tenase complex (FVIIa/TF). Herein, it was performed functional and structural evaluation of Amblyomin-X.
The CD assay and molecular dynamics simulations revealed that Amblyomin-X is structurally stable and the naturally unfolded
regions as well as the presence of three disulfide bridges in its Kunitz-type domain seem to sustain its inhibitory activity.
Regarding the electrostatic potential mapping on the Kunitz-type region, the pattern of charged residues was not
quite the same in comparison to human TFPI-1 and TFPI-2, pointing out there might be distinct functional and structural
features, which are going to be experimentally exploited.
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