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Chicken avidin exhibits pseudo-catalytic properties. Biochemical, structural, and electrostatic consequences
T Huberman1, Y Eisenberg-Domovich, G Gitlin
1Department of Biological Chemistry, The Institute of Life Sciences, Wolfson Centre for Applied Structural Biology, Hebrew University of Jerusalem, Givat Ram, Jerusalem 91904, Israel.
The Journal of Biological Chemistry
|June 8, 2001
Summary
Avidin enhances biotinyl p-nitrophenyl ester hydrolysis, while streptavidin protects it. Structural differences, including a flexible loop and specific amino acid interactions in avidin, explain this contrasting catalytic behavior.
Area of Science:
- Biochemistry and Molecular Biology
- Structural Biology
- Biotechnology
Background:
- Avidin and streptavidin are proteins with exceptionally high affinity for biotin, widely used in biotechnological applications.
- Despite structural similarities, avidin and streptavidin exhibit distinct biochemical properties.
- Understanding these differences can provide insights into protein catalysis and evolution.
Purpose of the Study:
- To investigate the differential effects of avidin and streptavidin on the alkaline hydrolysis of biotinyl p-nitrophenyl ester.
- To elucidate the structural basis for avidin's enhancement versus streptavidin's protection of this hydrolysis reaction.
- To explore implications for artificial protein catalysts and the evolution of catalytic sites.
Main Methods:
- Comparative analysis of avidin and streptavidin's influence on biotinyl p-nitrophenyl ester hydrolysis under alkaline conditions.
- Determination of three-dimensional crystal structures of avidin and streptavidin complexed with biotinyl p-nitroanilide.
- Analysis of molecular interactions and structural features contributing to catalytic enhancement or protection.
Main Results:
- Avidin enhances the alkaline hydrolysis of biotinyl p-nitrophenyl ester, whereas streptavidin protects it, even at pH > 12.
- The hydrolysis reaction proceeds as a single cycle due to the high affinity for the biotin product.
- Structural analysis revealed key features in avidin, including a flexible loop, arginine 114, and lysine 111 interactions, absent in streptavidin, which promote hydrolysis.
Conclusions:
- Specific molecular features in avidin's active site, such as its flexible loop and strategic amino acid residues, are responsible for enhancing biotinyl p-nitrophenyl ester hydrolysis.
- Streptavidin's lack of these features results in protection of the substrate from hydrolysis.
- These findings offer valuable insights into protein-based catalysis and the design of artificial enzymes.