Determination of the role of the Carboxyl-terminal leucine-122 in FMN-binding protein by mutational and structural analysisKitamura, M., Terakawa, K., Inoue, H., Hayashida, T., Suto, K., Morimoto, Y., Yasuoka, N., Shibata, N., Higuchi, Y.
(2007) J Biochem 141: 459-468
- PubMed: 17261542
- DOI: https://doi.org/10.1093/jb/mvm051
- Primary Citation of Related Structures:
1WLI, 1WLK, 3A20
- PubMed Abstract:
Mutants of flavin mononucleotide-binding protein (FMN-bp) were made by site-directed mutagenesis to investigate the role of carboxyl-terminal Leu122 of the pairing subunit in controlling redox potentials, binding the prosthetic group, and forming the tertiary and quaternary structure. We compared the oxidation-reduction potentials, FMN-binding properties, and higher structures of wild-type FMN-bp and four mutant proteins (L122Y, L122E, L122K and L122-deleted). We found that the redox potentials were affected by mutations. Also, the affinities of L122E, L122K and L122 deletion mutant apoproteins for FMN were lower than for the wild-type apoprotein, whereas the affinity of L122Y for FMN was increased. Analytical ultracentrifugation showed that the dissociation constants for dimerization of L122E and L122K were larger than for wild-type FMN-bp, whereas the dissociation constants for L122Y and the deletion mutant were lower than for the wild type. Finally, we determined the higher structures of L122Y, L122E and L122K mutants by X-ray crystallography. Our results show that the mutation of Leu122 in FMN-bp changes midpoint potentials, dissociation constants for FMN, and dimer formation, indicating that this residue is important in the pairing subunit.
Department of Applied and Bioapplied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto, Osaka, Japan. email@example.com