Archive for the ‘Plasma’ Category

Secreted Epididymal Glycoprotein: DISCUSSION(10)

In addition to 24 kDa/E-2, several other p-defensin-like molecules appear to be specific to the epididymis. These include Bin-1b in the rat and ESC42, hE2, and EP2 in primates. Of these, HE2 and Bin-1b have been shown to possess antimicrobial action in vitro. Interestingly, although ESC42 and ESP13.2 possess an N-ter-minal defensin-like domain, they share […]

Secreted Epididymal Glycoprotein: DISCUSSION(9)

Sequence Analysis of 2D6 Antigen and Preliminary Assignment of Functionality As mentioned earlier, a sequence analysis of the 24-kDa subunit purified from cauda spermatozoa revealed that it is identical to isoantigen E-2 and that it belongs to a family of small epididymal peptides, 68 to 123 residues long, that show significant sequence similarity to somatic […]

Secreted Epididymal Glycoprotein: DISCUSSION(8)

Both these properties are characteristic of hydrophobic interactions. If the antigen had bound covalently to an integral membrane receptor, then it would have migrated with a higher molecular mass after SDS-PAGE. That a significant proportion of 24-kDa antigen remains in the aqueous layer after detergent-phase separation suggests significant structural heterogeneity, conceivably mediated by differences in […]

Secreted Epididymal Glycoprotein: DISCUSSION(7)

Direct evidence for uptake of 2D6-reactive antigens from epididymal secretions was obtained by incubating proximal caput spermatozoa (which do not bind 2D6 McAb) in vitro with caudal fluid. Since neither rat erythrocytes nor lymphocytes stain positively with 2D6 McAb after incubation in caudal plasma, it suggests that uptake is cell-type specific and mediated either by […]

Secreted Epididymal Glycoprotein: DISCUSSION(6)

Binding of 2D6-Reactive Antigens to the Sperm Plasma Membrane In nearly all examples of secreted epididymal glycoproteins binding to the sperm surface, only qualitative information is available, whereas in the present work we have used FACS analysis to quantify the interaction between 2D6-reactive antigens and the sperm’s plasma membrane.

Secreted Epididymal Glycoprotein: DISCUSSION(5)

On the basis of the evidence presented here we cannot distinguish between these two hypotheses. However, during preparation of this work for publication we became aware of a sequence in the Genbank database describing a rat sperm isoantigen (designated E-3) that was identical to that for the 24-kDa antigen. A subsequent publication describing the cloning […]

Secreted Epididymal Glycoprotein: DISCUSSION(4)

An alternative hypothesis is that the 2D6 carbohydrate epitope is generic to several different glycoproteins that are secreted in different regions of the epididymis and that change their reactivity to the McAb during epididymal maturation. Thus, initially a —250-kDa component is secreted in the distal caput epididymidis that binds to spermatozoa in the lumen of […]

Secreted Epididymal Glycoprotein: DISCUSSION(3)

Characterization of Secreted and Membrane-Bound Forms of 2D6 antigen The demonstration that 2D6 McAb recognizes an O-linked carbohydrate epitope has important implications for identification of its cognate antigens in luminal fluid and on spermatozoa. One interpretation of the multiple bands on Western blots shown in Figure 3 is that 2D6 antigen is secreted in the […]

Secreted Epididymal Glycoprotein: DISCUSSION(2)

This evidence suggests that 2D6 antigen is secreted in a relatively dilute and soluble form by classic exocytotic pathways and is then concentrated in the luminal fluid by selective transport of water in the reverse direction. Gold particles in the lumen are usually associated with small electron-dense aggregates, and there is no indication that they […]

Secreted Epididymal Glycoprotein: DISCUSSION(1)

The major aims of this investigation were, first, to shed light on the mechanism of secretion of epididymal glycoproteins; second, to examine the mechanism of binding of specific glycoproteins to the sperm surface; and third, to elucidate their disposition within the plasma membrane. For this purpose we selected a McAb known as 2D6 that has […]

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