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Structure/function analysis of the sea urchin sperm adhesive protein bindin
A Lopez1, S J Miraglia, C G Glabe
1Department of Molecular Biology and Biochemistry, University of California, Irvine 92717.
Developmental Biology
|March 1, 1993
Summary
Sea urchin bindin protein mediates species-specific sperm-egg attachment. Its amino and carboxyl-terminal regions, not the central domain, dictate this specificity, with repeat sequences potentially playing a key role in species recognition.
Area of Science:
- Reproductive Biology
- Molecular Biology
- Marine Biology
Background:
- Bindin is a sea urchin sperm protein crucial for fertilization.
- It mediates species-specific sperm-egg adhesion and egg agglutination.
- Bindin binds to egg surface glycoconjugates.
Purpose of the Study:
- To analyze the functional domain structure of bindin.
- To identify regions responsible for species-specific binding.
- To investigate the role of repeat sequences in species recognition.
Main Methods:
- Recombinant bindin analogs with deletions were expressed in E. coli.
- Species-specific egg agglutination and sperm adhesion assays were performed.
- Amino acid sequences of bindin from different species were compared.
Main Results:
- S. franciscanus bindin agglutinates both S. franciscanus and S. purpuratus eggs.
- S. purpuratus bindin shows restricted specificity for S. purpuratus eggs.
- Deletion of N- or C-terminal residues (1-74 or 122-236) did not affect S. purpuratus bindin's specificity.
- The central domain (residues 75-121) is conserved, with minimal variation at Arg 77.
- Divergent N- and C-terminal sequences and repeat motifs are implicated in species specificity.
Conclusions:
- The amino- and carboxyl-terminal regions of bindin, not the central domain, determine species specificity.
- Either terminal region is sufficient to impart specificity.
- Variable repeat sequences in the termini may be critical for species recognition mechanisms.