Novel purification method for mammalian seminal plasma phospholipid-binding proteins reveals the presence of a novel member of this family of protein in stallion seminal fluid.

The research revolves around the development of a novel method for purifying phospholipid-binding proteins found in mammalian seminal fluid, which also revealed the presence of a new member of this protein type in stallion seminal fluid.

Method Development

• The researchers devised a new isolation method for purifying choline phospholipid-binding proteins which are a part of mammalian seminal plasma and are often found in low concentrations.
• This method relies on the interaction of these proteins with the egg yolk’s low-density lipoprotein fraction (LDF).
• As a part of the study, the team incubated LDF with alcohol precipitates from the seminal plasma of bulls, boars, and stallions.
• The LDF, along with bound proteins, were successfully re-isolated through ultracentrifugation.
• Post this, the LDF and associated proteins underwent dialysis, lyophilization, and delipidation.
• Finally, the homologous proteins of bull seminal plasma (BSP) were purified through p-aminophenyl phosphorylcholine (PPC)-agarose or gelatin-agarose chromatographies.
• The purified proteins were then scrutinized through SDS-PAGE, a common laboratory technique in biochemistry for the separation of proteins based on their electrophoretic mobility.

Recovery and Detection of New Protein

• Using this newly devised protocol, the team was able to recover nearly 100% phospholipid-binding proteins present in the seminal plasma of bulls, boars, and stallions.
• In the course of the study, the researchers also discovered and partially sequenced a novel 12 kDa protein in stallion seminal plasma which falls in the same family.
• The radioimmunoassay (RIA) data collected suggested that 10 mg of LDF is capable of binding all BSP proteins present in 120 mg of alcohol precipitated BSP proteins.

Significance of the Study

• The study’s findings improved the process of phospholipid-binding proteins isolation and confirmed the effectiveness of this new method.
• Moreover, the LDF step in the process proved to be beneficial for isolating all homologs of BSP proteins from various mammalian species.