Characterization and biological properties of L-HGP, a glycoprotein from the amphibian oviduct with acrosome-stabilizing effects.

KRAPF, D.; VIDAL, M.; ARRANZ, SILVIA EDA; CABADA, M.

BIOLOGY OF THE CELL

Año: 2006 vol. 98 p. 403 - 413

0248-4900

Background information. The role of the jelly coat that surrounds the amphibian oocytes has been widely discussed,but is poorly understood. The presence of the jelly coat is essential for fertilization. However, the structure and functionof the molecules that comprise the jelly coat have not been thoroughly documented. L-HGP (low-molecularmasshighly glycosylated protein) is a highly glycosylated protein that is present in the jelly coat of the toad, Bufoarenarum, oocytes and diffuses to the surrounding media. L-HGP, when purified from egg water, protects the spermacrosome from breakdown induced by hypotonic solutions.Results. L-HGP is an acidic glycoprotein, formed by two different subunits, linked by disulphide bonds. We raisedpolyclonal antibodies in rabbits against the deglycosylated protein. We determined that L-HGP is secreted alongthe oviduct, being hence present in all the jelly layers. The molecular mass of L-HGP is higher in the most cephalicregion of the oviduct. The lower-Mr L-HGP isoform, produced in the caudal regions of the oviduct, presents anacrosome-protecting property. L-HGP is produced by secretory cells in the oviduct and is deposited on the cilia atthe oviduct lumen.Conclusions. Biochemical characterization of L-HGP has been carried out. It is synthesized by secretory cells inthe oviduct and, when secreted, is deposited over the ciliated surface of the cells. The lower-Mr isoform, secretedby the caudal region of the oviduct, protects acrosome integrity. This isoform diffuses into the medium. The role ofthe higher-Mr L-HGP isoform in fertilization remains unknown.