1obv

File:1obv.gif

spinqualitylabelsall models 1obv, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Y94F FLAVODOXIN FROM ANABAENA

OverviewOverview

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.

About this StructureAbout this Structure

1OBV is a Single protein structure of sequence from Anabaena sp. with SO4 and FMN as ligands. Structure known Active Site: FMN. Full crystallographic information is available from OCA.

ReferenceReference

How FMN binds to anabaena apoflavodoxin: a hydrophobic encounter at an open binding site., Lostao A, Daoudi F, Irun MP, Ramon A, Fernandez-Cabrera C, Romero A, Sancho J, J Biol Chem. 2003 Jun 27;278(26):24053-61. Epub 2003 Apr 7. PMID:12682068

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