Interaction of milk proteins and Binder of Sperm (BSP) proteins from boar, stallion and ram semen

Geneviève Plante,Michel Lafleur,Puttaswamy Manjunath,Marie-France Lusignan

doi:10.1186/s12958-015-0093-1

Geneviève Plante, Michel Lafleur + Show 2 more

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https://doi.org/10.1186/s12958-015-0093-1

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Abstract

BackgroundMammalian semen contains a family of closely related proteins known as Binder of SPerm (BSP proteins) that are added to sperm at ejaculation. BSP proteins extract lipids from the sperm membrane thereby extensively modifying its composition. These changes can ultimately be detrimental to sperm storage. We have demonstrated that bovine BSP proteins interact with major milk proteins and proposed that this interaction could be the basis of sperm protection by milk extenders. In the present study, we investigated if homologous BSP proteins present in boar, stallion and ram seminal plasma display a similar affinity for the milk proteins in order to assess whether the mechanism of sperm protection by milk for these species could be general.MethodsSkim milk was incubated with seminal plasma proteins (boar, stallion and ram), chromatographed on a Sepharose CL-4B column and protein fractions were analyzed by immunoblotting.ResultsBoar, stallion and ram BSP proteins displayed affinity for a milk protein fraction (F1) mainly composed of α-lactalbumin, β-lactoglobulin, and κ-casein. They also had affinity for another milk protein fraction (F2) composed mostly of casein micelles. However, stallion BSP showed higher affinity for the fraction (F1).ConclusionsThese results further extend our view that the association of BSP proteins with milk proteins could be a general feature of the mechanism of mammalian sperm protection by milk to prevent detrimental effect of prolonged exposure of sperm to seminal plasma.

Highlights

Mammalian semen contains a family of closely related proteins known as Binder of SPerm (BSP proteins) that are added to sperm at ejaculation
We previously demonstrated that the low-density lipoproteins (LDL) of Egg yolk (EY) interact with BSP proteins and that this interaction prevents cholesterol and phospholipid extraction from the sperm membrane, thereby protecting sperm during preservation
We previously showed that stallion seminal plasma contains a group of BSP proteins with molecular mass of 12 kDa, 15–18 kDa, and 22–24 kDa [18]

Summary

Introduction

Mammalian semen contains a family of closely related proteins known as Binder of SPerm (BSP proteins) that are added to sperm at ejaculation. BSP proteins extract lipids from the sperm membrane thereby extensively modifying its composition These changes can be detrimental to sperm storage. Bovine seminal plasma contains a family of proteins designated as Binder of SPerm (BSP) proteins, which have been extensively characterized [3,4,5,6]. These proteins positively modulate the induction of sperm capacitation, a process that is deemed to be essential for fertilization [7, 8]. We previously demonstrated that the low-density lipoproteins (LDL) of EY interact with BSP proteins and that this interaction prevents cholesterol and phospholipid extraction from the sperm membrane, thereby protecting sperm during preservation (reviewed in [2])

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