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


METHODS
Skim 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.


RESULTS
Boar, 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).


CONCLUSIONS
These 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.
Department of Medicine, Université de Montréal, C.P. 6128, Succ. Centre Ville, Montréal, Québec, Canada, H3C 3J7. genevieve.plante@umontreal.ca.|Maisonneuve-Rosemont Hospital Research Center, 5415 L'Assomption blvd, Montréal, Québec, Canada, H1T 2M4. genevieve.plante@umontreal.ca.
Geneviève
G
Plante
Department of Medicine, Université de Montréal, C.P. 6128, Succ. Centre Ville, Montréal, Québec, Canada, H3C 3J7. lusignanmf@sympatico.ca.|Maisonneuve-Rosemont Hospital Research Center, 5415 L'Assomption blvd, Montréal, Québec, Canada, H1T 2M4. lusignanmf@sympatico.ca.
Marie-France
MF
Lusignan
Department of Chemistry, Center for Self-Assembled Chemical Structures, Université de Montréal, C.P. 6128, Succ. Centre Ville, Montréal, Québec, Canada, H3C 3J7. michel.lafleur@umontreal.ca.
Michel
M
Lafleur
Department of Medicine, Université de Montréal, C.P. 6128, Succ. Centre Ville, Montréal, Québec, Canada, H3C 3J7. puttaswamy.manjunath@umontreal.ca.|Maisonneuve-Rosemont Hospital Research Center, 5415 L'Assomption blvd, Montréal, Québec, Canada, H1T 2M4. puttaswamy.manjunath@umontreal.ca.|Puttaswamy Manjunath, Maisonneuve-Rosemont Hospital Research Center, 5415 L'Assomption blvd, Montréal, Québec, Canada, H1T 2M4. puttaswamy.manjunath@umontreal.ca.
Puttaswamy
P
Manjunath
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D006736:Horses; D008297:Male; D008894:Milk Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000502:physiology; D012661:Semen / Q000378:metabolism*; D029607:Seminal Vesicle Secretory Proteins / Q000235:genetics / Q000378:metabolism*; D012756:Sheep; D013045:Species Specificity; D034421:Sus scrofa
C519889:BSPH1 protein, human; C519891:Bsph2 protein, mouse; D008894:Milk Proteins; D029607:Seminal Vesicle Secretory Proteins