1OBV

Y94F flavodoxin from Anabaena

Summary for 1OBV

• Entry DOI: 10.2210/pdb1obv/pdb
• Related: 1DX9 1FLV 1FTG 1OBO 1QHE 1RCF
• Descriptor: FLAVODOXIN, FLAVIN MONONUCLEOTIDE, SULFATE ION, ... (4 entities in total)
• Functional Keywords: electron transfer, flavoprotein, electron transport
• Biological source: ANABAENA SP.
• Total number of polymer chains: 1
• Total formula weight: 19560.06

Authors

Romero, A.,Ramon, A.,Fernandez-Cabrera, C.,Irun, M.P.,Sancho, J. (deposition date: 2003-01-31, release date: 2003-04-24, Last modification date: 2023-12-13)

Primary citation

Lostao, A.,Daoudi, F.,Irun, M.P.,Ramon, A.,Fernandez-Cabrera, C.,Romero, A.,Sancho, J.
How Fmn Binds to Anabaena Apoflavodoxin: A Hydrophobic Encounter at an Open Binding Site
J.Biol.Chem., 278:24053-, 2003

PubMed Abstract: Molecular recognition begins when two molecules approach and establish interactions of certain strength. The mechanisms of molecular recognition reactions between biological molecules are not well known, and few systems have been analyzed in detail. We investigate here the reaction between an apoprotein and its physiological cofactor (apoflavodoxin and flavin mononucleotide) that binds reversibly to form a non-covalent complex (flavodoxin) involved in electron transfer reactions. We have analyzed the fast binding reactions between the FMN cofactor (and shorter analogs) and wild type (and nine mutant apoflavodoxins where residues interacting with FMN in the final complex have been replaced). The x-ray structures of two such mutants are reported that show the mutations are well tolerated by the protein. From the calculated microscopic binding rate constants we have performed a Phi analysis of the transition state of complex formation that indicates that the binding starts by interaction of the isoalloxazine-fused rings in FMN with residues of its hydrophobic binding site. In contrast, the phosphate in FMN, known to contribute most to the affinity of the final holoflavodoxin complex, is not bound in the transition state complex. Both the effects of ionic strength and of phosphate concentration on the wild type complex rate constant agree with this scenario. As suggested previously by nmr data, it seems that the isoalloxazine-binding site may be substantially open in solution. Interestingly, although FMN is a charged molecule, electrostatic interactions seem not to play a role in directing the binding, unlike what has been reported for other biological complexes. The binding can thus be best described as a hydrophobic encounter at an open binding site.

PubMed: 12682068
DOI: 10.1074/JBC.M301049200

Experimental method

X-RAY DIFFRACTION (2.1 Å)