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Crystal structure of chicken riboflavin-binding protein
1Department of Genetics, University of Pavia, Italy.
The EMBO Journal
|April 1, 1997
Summary
The crystal structure of chicken egg white riboflavin-binding protein reveals a unique fold stabilized by disulfide bridges and a phosphorylated motif crucial for vitamin uptake. This structure explains riboflavin binding and fluorescence quenching.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Biophysics
Background:
- Chicken egg white riboflavin-binding protein (REBP) is a prototype for a protein family binding riboflavin and folate.
- Avian REBP exhibits extensive disulfide cross-linking and a unique phosphorylated polypeptide chain.
Purpose of the Study:
- To determine and characterize the crystal structure of chicken egg white REBP.
- To elucidate the structural basis for ligand binding and the role of the phosphorylated motif.
Main Methods:
- X-ray crystallography at 2.5 A resolution.
- Structural analysis of protein-ligand interactions.
Main Results:
- The REBP structure comprises a ligand-binding domain and a phosphorylated motif.
- The ligand-binding domain's fold is influenced by disulfide bridges.
- The phosphorylated motif, with two helices, is essential for vitamin uptake.
- Riboflavin binds via its isoalloxazine ring between Tyr75 and Trp156, causing fluorescence quenching.
Conclusions:
- The determined crystal structure provides insights into the REBP family's architecture.
- Disulfide bridges and phosphorylation play critical roles in REBP structure and function.
- The binding site geometry explains riboflavin-induced fluorescence quenching.