Egg envelope conversion following fertilization in Bufo japonicus.
The envelope of the Bufo japonicus egg becomes impenetrable to sperm following fertilization. Electrophoretic analysis of envelopes showed that two glycoprotein components with apparent molecular weights of 65,000 and 61,000 were hydrolyzed during fertilization to 62,000 and 58,000, respectively. These two envelope components were structurally related as shown by peptide mapping and deglycosylation studies. Hardening of the envelope following egg activation was also observed, as detected by an increase in the envelope melting temperature. The involvement of proteolytic activities in the envelope hydrolysis and hardening reactions was demonstrated using protease inhibitors, and was verified for the hydrolysis reaction by observing a loss of mass in deglycosylated envelope components obtained before and after fertilization. A low ionic strength medium (less than 50 mM) was required for both the hardening and hydrolysis reactions. Envelopes from eggs activated in a high ionic strength medium were resistant to lysin from sperm, indicating that neither hydrolysis nor hardening was necessary to block lysin activity on the envelope. Both envelope hydrolysis and hardening could be effected in the absence of sperm (i.e., when eggs were activated by electric shock) and after egg jelly had been removed, indicating that neither sperm nor jelly factors were required for the envelope modifications. In addition, when eggs were activated in the presence of NH4Cl to suppress cortical granule exocytosis, envelope hardening and hydrolysis were still observed, indicating that a cortical granule-derived factor may not be involved.
Lindsay
L L
LL
Department of Biochemistry and Biophysics, University of California, Davis 95616.
Yamasaki
H
H
Hedrick
J L
JL
Katagiri
C
C
D000818:Animals; D002025:Bufonidae / Q000502:physiology*; D003594:Cytoplasmic Granules / Q000502:physiology; D004527:Egg Proteins / Q000378:metabolism*; D005306:Fertilization; D006868:Hydrolysis; D008297:Male; D008970:Molecular Weight; D009088:Mucoproteins / Q000378:metabolism; D010063:Ovum / Q000502:physiology* / Q000648:ultrastructure; D010449:Peptide Mapping; D011480:Protease Inhibitors / Q000494:pharmacology; D013094:Spermatozoa / Q000201:enzymology; D013696:Temperature; D013997:Time Factors
D004527:Egg Proteins; D009088:Mucoproteins; D011480:Protease Inhibitors; C010393:lysin, gastropoda