How Fmn Binds to Anabaena Apoflavodoxin: A Hydrophobic Encounter at an Open Binding Site

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