Conformational Analysis of Rat Seminal Vesicle Secretory Protein 4, an Intrinsically Disordered Protein Having Interesting Pharmacological Properties

Rat seminal vesicle protein 4 (RSV4) is a member of the seminal vesicle protein family present in rats, 90 residues long. When secreted, it is involved in many functions related to the reproduction ranging from semen coagulation to sperm capacitation, but its fragments have also shown in vitro pharmacological properties such as anti-inflammatory and pro-coagulant activity, important in the cancer development. However, no three-dimensional model of this protein is yet available probably because of the presence of intrinsic disorder in the structure. In this article we report structural studies in solution of RSV4 by SEC (size exclusion chromatography) and CD (circular dichroism). In solution the monomer is highly flexible and poorly organized with the presence of highly fluctuating helical segments and, as also suggested by SEC, is classifiable as NU-PMG (natively unfolded pre-molten globule). The lack of a cooperative sigmoidal structural transition induced by thermal and GdmCl perturbation in monomer supports the poor structural organization expected for a NU-PMG conformational model. The structure of RSV4 monomer was modeled computationally and subjected to molecular dynamics simulations to study its conformational changes and energetic stability.