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Electron transfer in a human inducible nitric oxide synthase oxygenase/FMN construct co‐expressed with the N‐terminal globular domain of calmodulin
Author(s) -
Feng Changjian,
Fan Weihong,
Dupont Andrea,
Guy Guillemette J.,
Ghosh Dipak K.,
Tollin Gordon
Publication year - 2010
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2010.09.028
Subject(s) - calmodulin , chemistry , heme , nitric oxide synthase , flavodoxin , flash photolysis , oxygenase , kinetics , electron transfer , stereochemistry , biophysics , biochemistry , photochemistry , reaction rate constant , enzyme , biology , ferredoxin , physics , quantum mechanics
The FMN‐heme intraprotein electron transfer (IET) kinetics in a human inducible NOS (iNOS) oxygenase/FMN (oxyFMN) construct co‐expressed with NCaM, a truncated calmodulin (CaM) construct that includes only its N‐terminal globular domain consisting of residues 1–75, were determined by laser flash photolysis. The IET rate constant is significantly decreased by nearly fourfold (compared to the iNOS oxyFMN co‐expressed with full length CaM). This supports an important role of full length CaM in proper interdomain FMN/heme alignment in iNOS. The IET process was not observed with added excess EDTA, suggesting that Ca 2+ depletion results in the FMN domain moving away from the heme domain. The results indicate that a Ca 2+ ‐dependent reorganization of the truncated CaM construct could cause a major modification of the NCaM/iNOS association resulting in a loss of the IET.