DSP-1, the major fibronectin type-II protein of donkey seminal plasma is a small heat-shock protein and exhibits chaperone-like activity against thermal and oxidative stress.

This research article explores the properties of a major protein found in donkey seminal plasma, suggested to play an important role in sperm capacitation, known as DSP-1. The study shows that DSP-1 exhibits chaperone-like activity (CLA), protecting proteins against thermal and oxidative stress, which can be influenced by specific binding interactions. The findings contribute to the understanding of how seminal proteins function in mammals.

The Role of DSP-1

• The research primarily focuses on DSP-1, or fibronectin type-II (FnII) protein – a major component of donkey seminal plasma.
• Fibronectin type-II proteins are crucial in many mammalian species for sperm capacitation – the maturation process that sperm undergo to be able to fertilize an egg.

Chaperone-Like Activity of DSP-1

• The study reveals that DSP-1 exhibits chaperone-like activity (CLA) – it acts as a small heat shock protein (shsp), protecting other proteins from damage caused by thermal and oxidative stress.
• Examples of proteins that are protected by DSP-1, according to the study, include alcohol dehydrogenase, lactate dehydrogenase, and enolase.
• DSP-1 follows the pattern seen in similar proteins derived from the seminal fluid of bulls and horses, which are also noted to have CLA.

Effect of Ligand Binding on DSP-1 CLA

• The research notes that when DSP-1 binds with phosphorylcholine (PrC), a choline phospholipid, its CLA decreases. On the other hand, its CLA increases when it binds with 1,2-dioleoyl-sn-glycero-3-phospholcholine (DOPC).
• This binding effect, researchers propose, could be due to changes in the surface hydrophobicity (or ability to mix with water) of DSP-1 when these ligands are bound.
• PrC binding results in transforming DSP-1 tetramers (groupings of four protein molecules) into monomers (single molecules) with lower surface hydrophobicity.
• DOPC liposome binding, interestingly, increases the protein’s surface hydrophobicity – encouraging CLA.

Implications of the Study

• The study’s findings provide valuable insights into the role of seminal plasma proteins in mammalian reproduction processes, specifically highlighting the versatile utility of DSP-1 as a molecular chaperone.
• Demonstration of DSP-1’s chaperone-like function expands the understanding of mammalian FnII protein varieties that can operate as small heat shock proteins, thereby enhancing CLA and ability to guard other proteins against potentially damaging stress.