Zona pellucida glycoprotein 3 (ZP3) has been ascribed as a putative primary sperm receptor during fertilization in humans. Herein, attempts have been made to delineate the functional domain of human ZP3. ZP3 has been cloned and expressed in a baculovirus expression system as N-terminal fragments (amino acid [aa] residues 1–175 [pAc-ZP3(1–175 aa)] and 23–175 [pBg-ZP3(23–175 aa)]) and as C-terminal fragments (aa residues 214–305 [pBg-ZP3(214–305 aa)] and 214–348 [pBg-ZP3(214–348 aa)]). ZP3 encompassing both N- and C-terminal fragments corresponding to aa residues 1–370 (pAc-ZP3[1–370 aa]) has also been expressed. Lectin-binding analysis with these recombinant proteins revealed the presence of N- and O-linked glycosylation. Significant induction of acrosomal exocytosis was observed when capacitated sperm were incubated with pBg-ZP3(214–348 aa), pBg-ZP3(214–305 aa), and pAc-ZP3(1–370 aa) (P < 0.05), whereas incubation with pAc-ZP3(1–175 aa) and pBg-ZP3(23–175 aa) failed to do so under similar experimental conditions. However, N- and C-terminal fragments labeled with fluorescein isothiocyanate revealed binding to the anterior head of capacitated human spermatozoa. Escherichia coli-expressed ZP3 C-terminal fragments and chemically deglycosylated pBg-ZP3(214–348 aa) failed to induce a significant (P > 0.05) increase in acrosomal exocytosis, suggesting the relevance of glycosylation in imparting functional activity to ZP3 C-terminal fragments. pBg-ZP3(214–348 aa)-mediated induction of acrosomal exocytosis is regulated by Gi protein, extracellular calcium, GABA(A) [gamma aminobutyric acid (A)] receptor-mediated Cl− channel, and T-type voltage-operated calcium channels. Taken together, the results of these studies suggest that the functional activity of human ZP3 resides in its C-terminal domain.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.