title: Biophysical investigations on the interaction of the major bovine seminal plasma protein, PDC-109, with heparin.
abstract: PDC-109, the major bovine seminal plasma protein, binds to sperm plasma membrane and modulates capacitation in the presence of heparin. In view of this, the PDC-109/heparin interaction has been investigated employing various biophysical approaches. Isothermal titration calorimetric studies yielded the association constant and changes in enthalpy and entropy for the interaction at 25 °C (pH 7.4) as 1.92 (±0.2) × 10(5) M(-1), 18.6 (±1.6) kcal M(-1), and 86.5 (±5.1) cal M(-1) K(-1), respectively, whereas differential scanning calorimetric studies indicated that heparin binding results in a significant increase in the thermal stability of PDC-109. The affinity decreases with increase in pH and ionic strength, consistent with the involvement of electrostatic forces in this interaction. Circular dichroism spectroscopic studies indicated that PDC-109 retains its conformational features even up to 70-75 °C in the presence of heparin, whereas the native protein unfolds at about 55 °C. Atomic force microscopic studies demonstrated that large oligomeric structures are formed upon binding of PDC-109 to heparin, indicating an increase in the local density of the protein, which may be relevant to the ability of heparin to potentiate PDC-109 induced sperm capacitation.
authors.affiliation: School of Chemistry, University of Hyderabad, Hyderabad, India.
authors.forename: Rajeshwer S
authors.initials: RS
authors.lastname: Sankhala
authors.forename: Rajani S
authors.initials: RS
authors.lastname: Damai
authors.forename: V
authors.initials: V
authors.lastname: Anbazhagan
authors.forename: C Sudheer
authors.initials: CS
authors.lastname: Kumar
authors.forename: Gopalakrishnan
authors.initials: G
authors.lastname: Bulusu
authors.forename: Musti J
authors.initials: MJ
authors.lastname: Swamy
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D002417:Cattle; D006493:Heparin / Q000378:metabolism*; D008297:Male; D009994:Osmolar Concentration; D010767:Phosphorylcholine / Q000378:metabolism; D011485:Protein Binding; D011489:Protein Denaturation; D055503:Protein Multimerization; D055550:Protein Stability; D029607:Seminal Vesicle Secretory Proteins / Q000737:chemistry / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D029607:Seminal Vesicle Secretory Proteins; C424303:seminal vesicle secretory protein 109, Bos taurus; D010767:Phosphorylcholine; D006493:Heparin