Modulation of chaperone-like and membranolytic activities of major horse seminal plasma protein HSP-1/2 by L-carnitine.

The major protein of horse seminal plasma, HSP-1/2, exhibits membranolytic and chaperone-like activities and plays a crucial role in regulating sperm capacitation. L-Carnitine is a small polar molecule present in high concentrations in mammalian seminal plasma. The present results demonstrate that L-carnitine binds to HSP-1/2 and increases its thermal stability, enhances cooperativity of its chemical unfolding and decreases both chaperone-like and membranolytic activities of this protein. The HSP-1/2-L-carnitine complex exhibits anti-oxidative behaviour by inhibiting the production of hydroxyl radicals, suggesting that it can protect other constituents of seminal plasma from damage by hydroxyl radicals. As HSP-1/2 and L-carnitine share the same spatiotemporal location in the horse reproductive tract, this interaction is physiologically significant and may prevent premature interaction of HSP-1/2 with sperm, which in turn regulates the sperm capacitation.