Dissecting the energetics of the apoflavodoxin-FMN complex
| Autor: | Mohamed El Harrous, Anabel Lostao, Antonio A. Romero, Javier Sancho, Fatna Daoudi, Antonio Parody-Morreale |
|---|---|
| Přispěvatelé: | Diputación General de Aragón, Lostao, Anabel, Romero, Antonio, Parody-Morreale, Antonio, Sancho, Javier, Lostao, Anabel [0000-0001-7460-5916], Romero, Antonio [0000-0002-6990-6973], Parody-Morreale, Antonio [0000-0002-4790-1610], Sancho, Javier [0000-0002-2879-9200] |
| Rok vydání: | 2000 |
| Předmět: |
Models
Molecular animal structures Flavodoxin Flavin Mononucleotide Binding energy Flavin mononucleotide Flavoprotein Calorimetry Crystallography X-Ray Biochemistry Hydrophobic effect chemistry.chemical_compound Gill titration calorimeter Lumiflavin Binding site Molecular Biology Anabaena-7120 DNA Primers Site-directed mutagenesis biology Base Sequence Molecular Structure Proteins Cell Biology Binding Refinement Binding constant Oxidized flavodoxin Crystallography chemistry Heat-capacity biology.protein Mutagenesis Site-Directed Thermodynamics Resolution Apoproteins Protein Binding |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| ISSN: | 0021-9258 |
| Popis: | 10 p.-5 fig.-8 tab. Many flavoproteins are non-covalent complexes between FMN and an apoprotein. To understand better the stability of flavoproteins, we have studied the energetics of the complex between FMN and the apoflavodoxin from Anabaena PCC 7119 by a combination of site-directed mutagenesis, titration calorimetry, equilibrium binding constant determinations, and x-ray crystallography. Comparison of the strength of the wild type and mutant apoflavodoxin-FMN complexes and that of the complexes between wild type apoflavodoxin and shortened FMN analogues (riboflavin and lumiflavin) allows the dissection of the binding energy into contributions associated with the different parts of the FMN molecule. The estimated contribution of the phosphate is greatest, at 7 kcal mol(-1); that of the isoalloxazine is of around 5-6 kcal mol(-1) (mainly due to interaction with Trp-57 and Tyr-94 in the apoprotein) and the ribityl contributes least: around 1 kcal mol(-1). The stabilization of the complex is both enthalpic and entropic although the enthalpy contribution is dominant. Both the phosphate and the isoalloxazine significantly contribute to the enthalpy of binding. The ionic strength does not have a large effect on the stability of the FMN complex because, although it weakens the phosphate interactions, it strengthens the isoalloxazine-protein hydrophobic interactions. Phosphate up to 100 mM does not affect the strength of the riboflavin complex, which suggests the isoalloxazine and phosphate binding sites may be independent in terms of binding energy. Interestingly, we find crystallographic evidence of flexibility in one of the loops (57-62) involved in isoalloxazine binding. This work was supported by Grants PB96-1439, PB97-1027, and PB97-1237 (Dirección General de Enseñanza Superior, Spain) and Grant P15/97 (Consejo Superior de I+ D, Diputación General de Aragón, Spain). |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|