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Query: UNIPROT:P56851 (epididymal)
 11,273 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Confluent monolayers of microvascular endothelial cells, derived from the rat epididymal fat pad and grown in culture, were radioiodinated by using the lactoper-oxidase method. Their radioiodinated surface polypeptides were detected by NaDodSO4/PAGE (followed by autoradiography) and were characterized by both lectin affinity chromatography and protease digestion to identify the proteins involved in albumin binding. All detected polypeptides were sensitive to Pronase digestion, whereas several polypeptides were resistant to trypsin. Pronase treatment of the cell monolayer significantly reduced the specific binding of radioiodinated rat serum albumin, but trypsin digestion did not. Limax flavus, Ricinus communis, and Triticum vulgaris agglutinins competed significantly with radioiodinated rat serum albumin binding, whereas other lectins did not. A single 60-kDa glyco-protein was precipitated in common by these three lectins and was trypsin-resistant and Pronase-sensitive. Rat serum albumin affinity chromatography columns weakly but specifically bound a 60-kDa polypeptide from cell lysates derived from radioiodinated cell monolayers. These findings indicate that the 60-kDa glycoprotein is directly involved in a specific interaction of albumin with the cultured microvascular endothelial cells used in these experiments.
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PMID:Albumin interacts specifically with a 60-kDa microvascular endothelial glycoprotein. 341 25

The ejaculated porcine spermatozoa were fractionated into the cytosol, membrane, midpiece plus tail (flagella) and head fractions, and their adenylate cyclase activities were measured. About 65% of the total activity was located in the flagella fraction. For all the fractions, Mn2+-dependent adenylate cyclase activity was about 20 times higher than Mg2+-dependent activity, and guanine nucleotides, fluoride, and other reagents tested did not activate adenylate cyclase. The results suggest that the GTP-dependent regulatory subunit is absent in porcine spermatozoa. The porcine seminal plasma was found to stimulate the adenylate cyclase activity in spermatozoa. The stimulating factor in porcine seminal plasma was partially purified by gel filtration and the molecular weight of the factor appeared to be between 200 and 300. The partially purified factor is heat stable and is not inactivated by treatment with Pronase, trypsin, phospholipase A2 or D but is inactivated by acid hydrolysis. It is easily soluble in water, partially soluble in methanol, and insoluble in ethanol, ethyl ether, chloroform, or acetone. The activation of sperm adenylate cyclase by the factor occurred without a time lag. The activating effect was dose-dependent, saturated at high dose, and ascribed to the increase of the maximal velocity (Vmax). The effect of the factor appears to be limited to adenylate cyclase in spermatozoa; the factor activated adenylate cyclase both in porcine and bovine spermatozoa but failed to activate those in other porcine tissues. The factor was shown to activate the enzyme not only in the ejaculated spermatozoa but also in the epididymal sperm. The factor was also found to elevate the cAMP level in the intact porcine spermatozoa. The factor enhanced the motility of corpus and cauda epididymal spermatozoa. These findings indicate the possibility that this factor initiates the spermatozoan motility upon ejaculation through directly activating adenylate cyclase.
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PMID:Activation of spermatozoan adenylate cyclase by a low molecular weight factor in porcine seminal plasma. 663 Feb 19

Fertilizing capacity among uterine-capacitated rabbit sperm cells declined exponentially during incubation with membrane vesicles from seminal plasma. In suspensions containing an average of 0.42 mg vesicle protein/10(6) sperm, decapacitation occurred with a half-time of 23 min (ki (native vesicles) = 1.78 +/- 0.14 h-1). Exposing these membrane vesicles to pronase retarded decapacitation, prolonging its half-time to 51 min (ki (pronase-digested vesicles) = 0.81 +/- 0.06 h-1). Cholesterol-bearing liposomes suppressed sperm-fertilizing capacity at a comparable rate. In suspensions containing an average of 0.52 mg lipid/10(6) sperm, decapacitation had a half-time also of 51 min (ki (liposomes) = 0.82 +/- 0.14 h-1). These lower inhibition rates accompanied diminished rates of vesicle uptake by spermatozoa. Membrane vesicles labeled with phosphatidyl[14C]choline rapidly bound to epididymal sperm cells, displaying a half-time of 2.3 min (ka (native vesicles) = 18.0 +/- 0.35 h-1). Following pronase treatment, this interval increased to 17 min (ka (pronase-digested vesicles) = 2.48 +/- 0.37 h-1). Liposome binding data yielded a half-time of 28 min (ka (liposomes) = 1.47 +/- 0.17 h-1). Postbinding decapacitation half-times for these vesicles, given by the difference between binding and decapacitation intervals, appear broadly alike: native vesicles, 21 min, pronase-digested vesicles, 34 min, and liposomes, 23 min. During this interval, a vesicle antifusigen (cholesterol) apparently transfers to the sperm plasma membrane inhibiting the acrosome reaction. The lipid bilayer in these membrane vesicles withstood proteolytic attack, as seen by electron microscopy. Pronase acted principally to hydrolyze vesicle glycoproteins, which evidently bind to the sperm surface during decapacitation.
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PMID:Binding by glycoproteins of seminal plasma membrane vesicles accelerates decapacitation in rabbit spermatozoa. 682 56