Site-Directed Mutagenesis of Phe 97 to Glu in Amicyanin Alters the Electronic Coupling for Interprotein Electron Transfer from Quinol Methylamine Dehydrogenase
| Autor: | Zhenyu Zhu, Victor L. Davidson, Limei Hsu Jones |
|---|---|
| Rok vydání: | 1998 |
| Předmět: |
Amicyanin
Stereochemistry Phenylalanine Glutamic Acid Photochemistry Biochemistry Cofactor Electron Transport chemistry.chemical_compound Residue (chemistry) Electron transfer Reaction rate constant Bacterial Proteins Metalloproteins Tryptophan tryptophylquinone Methylamine dehydrogenase Site-directed mutagenesis Paracoccus denitrificans Oxidoreductases Acting on CH-NH Group Donors biology Temperature Models Chemical chemistry Mutagenesis Site-Directed biology.protein Thermodynamics Oxidation-Reduction |
| Zdroj: | Biochemistry. 37:7371-7377 |
| ISSN: | 1520-4995 0006-2960 |
| DOI: | 10.1021/bi973020v |
| Popis: | Conversion by site-directed mutagenesis of Phe 97 of amicyanin to Glu significantly decreases the rate constant for the electron-transfer reaction from the quinol form of methylamine dehydrogenase to amicyanin. It is shown that the DeltaG degrees and reorganizational energy (lambda) associated with the electron-transfer reaction are unaffected by the mutation and that the decrease in the electron-transfer rate is attributable completely to a decrease in the electronic coupling matrix element (HAB). Phe 97 is not a part of the predicted pathway for electron-transfer from the tryptophan tryptophylquinone cofactor of MADH to the copper of amicyanin. The most likely explanation for these results is that the mutation of this residue at the protein-protein interface causes an increase in the interprotein distance within the protein complex. The change in distance necessary to cause the observed reduction of HAB is calculated assuming a range of beta values, and assuming either solely a direct distance dependence or a pathway dependence, for the long-range electron-transfer reaction. Thermodynamic analysis of the association constants for complex formation reveal that the reaction with the mutant amicyanin exhibits a large positive change in heat capacity whereas this is not observed in the reaction with the wild-type. This may be explained by the replacement of a hydrophobic residue with a polar residue at what is normally a hydrophobic protein-protein interface. The impact of these results on possible explanations for the relatively large reorganizational energy associated with this interprotein electron-transfer reaction is also discussed. |
| Databáze: | OpenAIRE |
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