In the crystal structure of a calmodulin (CaM)-bound @entity21890 domain of @entity1 inducible @entity842 synthase ( @entity3623 ), the CaM-binding region together with CaM forms a hinge, and pivots on an R536( @entity3623 )/E47(CaM) pair (Xia et al. J Biol Chem 284:30708-30717, 2009). Notably, isoform-specific @entity1 inducible @entity3623 S562 and C563 residues form @entity3884 bonds with the R536 residue through their backbone oxygens. In this study, we investigated the roles of the S562 and C563 residues in the @entity3623 @entity21890 - @entity1446 interdomain electron transfer (IET), the rates of which can be used to probe the interdomain @entity21890 / @entity1446 alignment. @entity1 inducible @entity3623 @entity69865 and @entity69866 mutants of an oxygenase/ @entity21890 (oxyFMN) construct were made by introducing charged residues at these sites as found in @entity1 neuronal @entity3623 and endothelial @entity3623 isoforms, respectively. The IET rate constant of the @entity69865 mutant is notably decreased by one third, and its @entity1785 fluorescence intensity per micromole per liter is diminished by approximately 24  %. These results suggest that a positive charge at position 562 destabilizes the @entity3884 -bond-mediated @entity3623 /CaM alignment, resulting in slower @entity21890 - @entity1446 IET in the mutant. On the other hand, the IET rate constant of the @entity69866 mutant is similar to that of the wild-type, indicating that the mutational effect is site-specific. Moreover, the @entity1 inducible @entity3623 oxyFMN @entity69867 mutant was constructed to disrupt the bridging CaM/ @entity3623 interaction, and its @entity21890 - @entity1446 IET rate was decreased by 96  %. These results demonstrated a new role of the isoform-specific @entity563 residue of the key CaM/ @entity21890 ( @entity3623 ) bridging site in regulating the @entity21890 - @entity1446 IET (possibly by tuning the alignment of the @entity21890 and @entity1446 domains).

Role of an isoform-specific XXXX residue in @entity21890 - @entity1446 electron transfer in inducible @entity842 synthase.

@entity1 :: ('9606', 'Species') :: ['human', 'Human'] @entity69866 :: ('p|SUB|C|563|R', 'ProteinMutation') :: ['C563R'] @entity3884 :: ('MESH:D006859', 'Chemical') :: ['hydrogen'] @entity1785 :: ('MESH:C024132', 'Chemical') :: ['flavin'] @entity69865 :: ('p|SUB|S|562|K', 'ProteinMutation') :: ['S562K'] @entity21890 :: ('342184', 'Gene') :: ['FMN'] @entity842 :: ('MESH:D009569', 'Chemical') :: ['nitric oxide'] @entity563 :: ('CHEBI:17822', 'Chemical') :: ['serine'] @entity3623 :: ('4843', 'Gene') :: ['NOS'] @entity69867 :: ('p|SUB|R|536|E', 'ProteinMutation') :: ['R536E'] @entity1446 :: ('MESH:D006418', 'Chemical') :: ['heme']
@entity563 :: (CHEBI:17822,Chemical) :: ['serine']
