Mechanism of egg envelope digestion by hatching enzymes, HCE and LCE in medaka, Oryzias latipes.
Hatching of medaka embryos from the fertilized egg envelope involves two enzymes, HCE and LCE. HCE swells the envelope and then LCE completely dissolves it. We determined HCE and LCE cleavage sites on the egg envelope that are primarily constructed of two groups of subunit proteins, ZI-1,2 and ZI-3. HCE and LCE cleaved different target sequences on the egg envelope proteins but shared one common cleavage site. HCE cleaved the N-terminal region of ZI-1,2 and ZI-3, mainly the Pro-Xaa-Yaa repeat sequence of ZI-1,2 into hexapeptides, but not the site within a zona pellucida (ZP) domain that is considered to be the core structure of the egg envelope. The cleavage of these N-terminal regions results in swelling and softening of the envelope. LCE cleaved the middle of the ZP domain of ZI-1,2, in addition to the upstream of the trefoil domain of ZI-1,2 and the ZP domain of ZI-3. This middle site is in the intervening sequence connecting two subdomains of the ZP domain. Cleaving this site would result in the solubilization of the swollen egg envelope by the disruption of the filamentous structure that is thought to be formed by the non-covalent polymerization of ZP domains.
Yasumasu
Shigeki
S
Department of Materials and Life Sciences, Faculty of Science and Technology, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo, Japan. s-yasuma@sophia.ac.jp
Kawaguchi
Mari
M
Ouchi
Satoshi
S
Sano
Kaori
K
Murata
Kenji
K
Sugiyama
Hitoshi
H
Akema
Tatsuo
T
Iuchi
Ichiro
I
D000595:Amino Acid Sequence; D000818:Animals; D004527:Egg Proteins / Q000235:genetics / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000502:physiology; D004798:Enzymes / Q000378:metabolism*; D029941:Fish Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009990:Oryzias / Q000196:embryology / Q000378:metabolism; D010063:Ovum / Q000166:cytology / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity
D004527:Egg Proteins; D004798:Enzymes; D029941:Fish Proteins; C092024:L-SF protein, Oryzias latipes; D011498:Protein Precursors; C104950:choriogenin H