Dicalcin inhibits fertilization through its binding to a glycoprotein in the egg envelope in Xenopus laevis

Naofumi Miwa, Motoyuki Ogawa, Yukiko Shinmyo, Yoshiki Hiraoka, Ken Takamatsu, Satoru Kawamura

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Fertilization comprises oligosaccharide-mediated spermegg interactions, including sperm binding to an extracellular egg envelope, sperm penetration through the envelope, and fusion with an egg plasma membrane. We show that Xenopus dicalcin, an S100-like Ca2+-binding protein, present in the extracellular egg envelope (vitelline envelope (VE)), is a suppressive mediator of sperm-egg interaction. Preincubation with specific antibody greatly increased the efficiency of in vitro fertilization, whereas prior application of exogenous dicalcin substantially inhibited fertilization as well as sperm binding to an egg and in vitro sperm penetration through the VE protein layer. Dicalcin showed binding to protein cores of gp41 and gp37, constituents of VE, in a Ca2+-dependent manner and increased in vivo reactivity of VE with a lectin, Ricinus communis agglutinin I, which was accounted for by increased binding ability of gp41 to the lectin and greater exposure of gp41 to an external environment. Our findings strongly suggest that dicalcin regulates the distribution of oligosaccharides within the VE through its binding to the protein core of gp41, probably by modulating configuration of oligosaccharides on gp41 and the three-dimensional structure of VE framework, and thereby plays a pivotal role in sperm-egg interactions during fertilization.

Original languageEnglish
Pages (from-to)15627-15636
Number of pages10
JournalJournal of Biological Chemistry
Issue number20
Publication statusPublished - 2010 May 14
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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