Structural origins of efficient proton abstraction from carbon by a catalytic antibody
| Autor: | Florian P. Seebeck, Donald Hilvert, Shuichiro Ito, Erik W. Debler, Ian A. Wilson, Andreas Heine |
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| Rok vydání: | 2005 |
| Předmět: |
Models
Molecular Protein Conformation Stereochemistry Recombinant Fusion Proteins Static Electricity Stacking Antibodies Catalytic In Vitro Techniques Crystallography X-Ray Catalysis Immunoglobulin Fab Fragments Mice chemistry.chemical_compound Animals Humans Moiety Carboxylate Bifunctional Multidisciplinary Hydrogen bond Leaving group Solvation Genetic Variation Biological Sciences Combinatorial chemistry Carbon Amino Acid Substitution chemistry Benzimidazoles Binding Sites Antibody Protons Haptens |
| Zdroj: | Proceedings of the National Academy of Sciences. 102:4984-4989 |
| ISSN: | 1091-6490 0027-8424 |
| Popis: | Antibody 34E4 catalyzes the conversion of benzisoxazoles to salicylonitriles with high rates and multiple turnovers. The crystal structure of its complex with the benzimidazolium hapten at 2.5-Å resolution shows that a combination of hydrogen bonding, π stacking, and van der Waals interactions is exploited to position both the base, Glu H50 , and the substrate for efficient proton transfer. Suboptimal placement of the catalytic carboxylate, as observed in the 2.8-Å structure of the Glu H50 Asp variant, results in substantially reduced catalytic efficiency. In addition to imposing high positional order on the transition state, the antibody pocket provides a highly structured microenvironment for the reaction in which the carboxylate base is activated through partial desolvation, and the highly polarizable transition state is stabilized by dispersion interactions with the aromatic residue Trp L91 and solvation of the leaving group oxygen by external water. The enzyme-like efficiency of general base catalysis in this system directly reflects the original hapten design, in which a charged guanidinium moiety was strategically used to elicit an accurately positioned functional group in an appropriate reaction environment and suggests that even larger catalytic effects may be achievable by extending this approach to the induction of acid-base pairs capable of bifunctional catalysis. |
| Databáze: | OpenAIRE |
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