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Liang et al. (1990) demonstrated that
the mouse Zp-2 gene contains 18 exons that range in size from 45 to
190 bp and are separated by 17 introns (81 to 1,490 bp). The gene
spans 12.1 kb of DNA. Zp-2 is transcribed and processed into a
2,201-nucleotide mRNA with very short 5-prime (30 nucleotide) and
3-prime (32 nucleotide) untranslated regions. Human ZP2 mRNA has a
single open reading frame initiated at an ATG that encodes a
polypeptide of 713 amino acids with a molecular weight of 80,217
daltons. The first 34 amino acids represent a signal peptide that
directs secretion; following cleavage, the resultant core polypeptide
is incorporated into the extracellular matrix. The ZP2 amino acid
sequence contains 7 potential N-linked glycosylation sites
(asn-X-ser/thr) and more than 100 potential O-linked glycosylation
sites.
ZP2 has been implicated as a secondary sperm receptor that binds
sperm only after the induction of the sperm acrosome reaction.
Immediately after fertilization, there are 2 major changes that
prevent polyspermy: a rapid electrical depolarization of the egg
plasma membrane that blocks additional sperm in the perivitelline
space from fusing with the egg, and biochemical modifications of the
zona pellucida. Both ZP2 and ZP3 (182889)
are modified by the zona reaction: ZP2 undergoes a proteolytic
cleavage and ZP3 loses its ability to induce the acrosome reaction
and its sperm receptor activity.
Victor A. McKusick : 6/5/1992
mark : 7/1/1997
terry : 5/5/1994
carol : 6/5/1992