3 research outputs found
Purification and Characterization of a Sperm Motility Inhibiting Factor from Caprine Epididymal Plasma
Several studies have been reported on the occurrence of sperm motility inhibiting factors in the male reproductive fluids of different mammalian species, but these proteins have not been adequately purified and characterized. A novel sperm motility inhibiting factor (MIF-II) has been purified from caprine epididymal plasma (EP) by Hydroxylapatite gel adsorption chromatography, DEAE-Cellulose ion-exchange chromatography and chromatofocusing. The MIF-II has been purified to apparent homogeneity and the molecular weight estimated by Sephacryl S-300 gel filtration is 160 kDa. MIF-II is a dimeric protein, made up of two subunits each having a molecular mass of 80 kDa as shown by SDS-PAGE. The isoelectric point of MIF-II is 5.1 as determined by chromatofocusing and isoelectric focusing. It is a heat labile protein and maximal active at the pH 6.9 to 7.5. The sperm motility inhibiting protein factor at 2 µg/ml (12.5 nM) level showed maximal motility-inhibiting activity. The observation that the epididymal plasma factor lowered the intracellular cAMP level of spermatozoa in a concentration-dependent manner suggests that it may block the motility of caprine cauda spermatozoa by interfering the cAMP dependent motility function. The results revealed that the purified protein factor has the potential of sperm motility inhibition and may serve as a vaginal contraceptive. The antibody raised against the MIF-II has the potential for enhancement of forward motility of cauda-spermatozoa. This antibody may thus be useful for solving some of the problems of male infertility due to low sperm motility
Synchronous Modulation of Cell Surface Lectin and Its Receptor in a Homologous Cell Population: A Novel Mechanism of Cellular Regulation
Testicular immotile sperm undergo maturation during epididymal transit when these cells
pass through caput, corpus, and cauda-epididymal regions. Maturing goat spermatozoa
specifically at the distal corpus epididymal stage show head-to-head autoagglutination
when incubated in vitro in a modified Ringer's solution. Here, we show the biochemical
mechanism of autoagglutination event and its functional significance. A lectin-like
molecule located on sperm surface specifically interacts with its receptor of the
neighboring homologous cells to cause autoagglutination. Lectin is a Ca++-dependent
galactose-specific protein. Failure of the pre- and post-distal corpus sperm to show
autoagglutination is due to lack of lectin-like molecule and its receptors, respectively.
Maturing sperm at distal corpus stage acquire lectin-like molecule followed by sharp
disappearance of its receptor, and this event is synchronously associated with the initiation
of sperm forward motility that is essential for fertilization in vivo. Lectin and its receptor
isolated from sperm plasma membrane showed high efficacy for blocking autoagglutination
phenomenon. The data are consistent with the view that synchronous modulation of
homologous cell surface lectin and their receptors constitutes a novel mechanism for
cellular regulation by generating waves of signals by manipulating lectin–sugar-dependent
“self-talk” and cell–cell “cross-talk”
Structural and Functional Characterization and Physiological Significance of a Stimulator Protein of Mg2+-independent Ca2+-ATPase Isolated from Goat Spermatozoa
Recently a low-molecular-mass protein purified
from goat testes cytosol has been reported from our
laboratory which is found to stimulate Mg2+-independent
Ca2+-ATPase without any significant effect on Mg2+-
dependent Ca2+-ATPase. In the present study, detailed
structural and functional characterization, as well as the
physiological significance of the protein has been described.
The stimulatory effect is found to be inhibited by known
inhibitors of P-type ATPases, vanadate and lanthanum
chloride. Monitoring of the phosphoenzyme intermediate by
autoradiography has shown that the stimulation of the
ATPase is due to the enhancement in the rate of dephosphorylation
of the overall reaction step. Along with the
stimulation of the enzyme activity, the protein is found to
enhance the calcium uptake. Amino acid analysis data show
that the stimulator contains about 26% non-polar amino acid
facilitating easy penetration to the hydrophobic core of the
membrane bound ATPase. Circular dichroism analysis of the
protein suggested the presence of all secondary structural
elements. The Western-blotting experiment shows its
expression level is the highest in goat testes. Peptide fragments
obtained in MALDI-MS analysis when subjected to
MSDB database search by MASCOT search engine reveals
that the proteins of close similarity with the protein under
study are actin related protein 2/3 complex subunit, peptidylprolyl
cis-trans isomerase and gastrin releasing peptide precursor. Besides, the protein under study is also shown to
decrease the forward motility of goat sperm without having
any significant effect on the total motility indicating its
possible role in fertility regulation