Identification and characterization of a sperm motility promoting glycoprotein from buffalo blood serum

Abstract

Early investigators reported the occurrence of unidentified protein factors in biological fluids that may regulate sperm motility essential for fertility potential. This study reports for the first time purification of a Forward Motility Stimulating Protein (FMSF‐I), to apparent homogeneity, from a biological fluid (buffalo blood serum) and its characterization. FMSF‐I is the major motility protein of buffalo serum: a rich source of the factor. FMSF showed high protein specificity and affinity for activating forward motility of goat cauda epididymal spermatozoa. The motility promoter at 0.5 μM level showed maximal activity when nearly 60%–70% of spermatozoa expressed forward motility. It is a 66 kDa monomeric acidic protein rich in aspartate, glutamate and leucine with isoelectric point of 3.7. FMSF: a Mg²⁺‐dependent protein binds to concanavalin A‐agarose and the glycoprotein nature of FMSF has been confirmed by PAS staining. The factor lost activity completely when treated with α‐mannosidase showing that the sugar part of the protein is essential for its biological activity. FMSF has no species specificity for its motility‐activating potential. Sperm surface has specific receptors of FMSF, which is strongly immunogenic. The factor is present in testis and epididymis although liver is its richest source. Motility promoting efficacy of FMSF is markedly higher than the well‐known non‐protein motility activators: theophylline and bicarbonate or their combination. FMSF is a physiological activator of sperm motility and as a slaughterhouse byproduct it has potentiality for solving some of the problems of animal breeding, conservation of endangered species, and human infertility: a global social problem.