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Ligand binding-induced conformational changes in riboflavin kinase: structural basis for the ordered mechanism
Subramanian Karthikeyan1, Qingxian Zhou, Andrei L Osterman
1Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Biochemistry
|October 29, 2003
Summary
Riboflavin kinase (RFK) phosphorylation of riboflavin to FMN involves significant conformational changes. New structural data reveals how RFK binds FMN and Mg2+, explaining its catalytic mechanism.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Riboflavin kinase (RFK) is crucial for synthesizing flavin cofactors FMN and FAD.
- Previous RFK structures lacked detailed insight into flavin binding and conformational dynamics.
Purpose of the Study:
- To elucidate the structural basis of human RFK's catalytic mechanism.
- To characterize the conformational changes upon flavin mononucleotide (FMN) binding.
Main Methods:
- X-ray crystallography of human RFK cocrystallized with MgADP and FMN.
- Analysis of enzyme-ligand interactions and conformational alterations.
Main Results:
- Human RFK undergoes significant conformational changes, particularly in Flap I and Flap II loops, upon FMN binding.
- FMN binding leads to extensive enzyme interactions and a novel Mg2+ coordination involving FMN phosphate.
- The catalytic base Glu86 is optimally positioned for phosphoryl transfer.
Conclusions:
- The study provides a structural rationale for the ordered kinetic mechanism of RFK.
- Understanding RFK's mechanism offers insights into flavin metabolism and potential therapeutic targets.