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An oocytic membrane receptor for biotin-binding protein
A V Vieira1, H B White, P M Vieira
1Department of Biochemistry, University of Alberta, Edmonton, Canada.
FEBS Letters
|March 11, 1996
Summary
Chicken oocytes contain a unique biotin-binding protein (BBP) in the yolk, also found in laying hen circulation. A BBP receptor on the oocyte membrane is crucial for binding, with estrogen regulating BBP levels.
Area of Science:
- Reproductive biology
- Molecular endocrinology
- Avian physiology
Background:
- Chicken oocytes accumulate a specific biotin-binding protein (BBP) in the yolk, distinct from egg white avidin.
- This yolk BBP is identical to a protein found in the circulation of laying hens.
Purpose of the Study:
- To investigate the presence and function of a biotin-binding protein (BBP) receptor in the chicken oocyte vitelline membrane.
- To determine the relationship between serum BBP levels, estrogen, and BBP receptor activity in laying hens.
Main Methods:
- Characterization of BBP and its receptor in chicken oocytes and serum.
- Experimental manipulation of the oocyte BBP receptor to assess binding activity.
- Analysis of serum BBP levels in relation to estrogen and sex (laying hens vs. roosters).
Main Results:
- The first evidence for a BBP receptor in the oocyte vitelline membrane is presented.
- Reduction of the 100 kDa receptor abolishes BBP-binding activity, indicating the necessity of a disulfide-bonded region.
- Serum BBP levels are strictly dependent on estrogen and are not detected in roosters.
- Circulatory BBP exhibits cognate binding to the oocyte membrane, potentially mediating endocytosis.
Conclusions:
- A specific BBP receptor on the oocyte vitelline membrane plays a role in BBP binding and uptake.
- Estrogen is a key regulator of circulating BBP levels in laying hens.
- The findings suggest a mechanism for endocytosis of estrogen-dependent circulatory BBP by the oocyte.