Document Detail

Role of neighboring FMN side chains in the modulation of flavin reduction potentials and in the energetics of the FMN:apoprotein interaction in Anabaena flavodoxin.
MedLine Citation:
PMID:  15568803     Owner:  NLM     Status:  MEDLINE    
Flavodoxins (Flds) are electron transfer proteins that carry a noncovalently bound flavin mononucleotide molecule (FMN) as a redox active center. A distinguishing feature of these flavoproteins is the dramatic change in the E(sq/rd) reduction potential of the FMN upon binding to the apoprotein (at pH 8.0, from -269 mV when free in solution to -438 mV in Anabaena Fld). In this study, the contribution of three neighboring FMN residues, Thr56, Asn58, and Asn97, and of three negatively charged surface residues, Glu20, Asp65, and Asp96, to modulate the redox properties of FMN upon its binding to the apoprotein has been investigated. Additionally, the role of these residues in the apoflavodoxin:FMN interaction has been analyzed. Concerning the redox potentials, the most noticeable result was obtained for the Thr56Gly mutant. In this Fld variant, the increased accessibility of FMN leads to an increase of +63 mV in the E(sq/rd) value. On the other hand, a correlation between the electrostatic environment of FMN and the E(sq/rd) has been observed. The more positive residues or the less negative residues present in the surroundings of the FMN N(1) atom, then the less negative the value for E(sq/rd). With regard to FMN binding to apoflavodoxin, breaking of hydrophobic interactions between FMN and residues 56, 58, and 97 seems to increase the K(d) values, especially in the Thr56Gly Fld. Such results suggest that the H-bond network in the FMN environment influences the FMN affinity.
Isabel Nogués; Luis Alberto Campos; Javier Sancho; Carlos Gómez-Moreno; Stephen G Mayhew; Milagros Medina
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Biochemistry     Volume:  43     ISSN:  0006-2960     ISO Abbreviation:  Biochemistry     Publication Date:  2004 Dec 
Date Detail:
Created Date:  2004-11-30     Completed Date:  2005-01-21     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  United States    
Other Details:
Languages:  eng     Pagination:  15111-21     Citation Subset:  IM    
Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias and Institute of Biocomputation and Physics of Complex Systems (BIFI), Universidad de Zaragoza, 50009-Zaragoza, Spain.
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MeSH Terms
Amino Acid Sequence
Anabaena / chemistry*,  genetics
Apoproteins / chemistry,  genetics,  metabolism*
Benzoquinones / chemistry,  metabolism
Computer Simulation
Electron Spin Resonance Spectroscopy
Flavin Mononucleotide / chemistry*
Flavins / chemistry,  metabolism*
Flavodoxin / biosynthesis,  chemistry*,  genetics,  isolation & purification
Models, Molecular
Molecular Sequence Data
Mutagenesis, Site-Directed
Spectrophotometry, Ultraviolet
Reg. No./Substance:
0/Apoproteins; 0/Benzoquinones; 0/Flavins; 0/Flavodoxin; 146-17-8/Flavin Mononucleotide; 3225-29-4/semiquinone radicals

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