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Structure of bacterial luciferase beta 2 homodimer: implications for flavin binding
J J Tanner1, M D Miller, K S Wilson
1Department of Biochemical and Biophysical Sciences, University of Houston, Texas 77204-5934, USA.
Biochemistry
|January 28, 1997
Summary
The crystal structure of Vibrio harveyi luciferase beta 2 homodimer reveals a novel FMNH2 binding site at the dimer interface, explaining reduced enzyme activity compared to the alpha beta form.
Area of Science:
- Biochemistry
- Structural Biology
- Enzymology
Background:
- Vibrio harveyi luciferase exists as alpha beta heterodimers and beta 2 homodimers.
- Understanding the structural basis for the differing activities of these forms is crucial.
Purpose of the Study:
- Determine the crystal structure of the beta 2 homodimer.
- Elucidate the structural differences and their functional implications compared to the alpha beta heterodimer.
Main Methods:
- X-ray crystallography (2.5 A resolution)
- Molecular replacement
- Structural homology analysis
- Biochemical evidence integration
Main Results:
- The beta 2 homodimer structure was determined, showing homology to the beta subunit of the alpha beta form.
- Resolved C-terminal residues and flipped peptide bonds were observed.
- A smaller dimer interface in beta 2 compared to alpha beta was identified.
- A potential FMNH2 binding pocket was located at the dimer interface, distinct from the proposed alpha beta binding site.
Conclusions:
- The beta 2 homodimer binds only one FMNH2 per homodimer at the dimer interface.
- Reduced FAD and riboflavin are predicted to be poor substrates for beta 2.
- Lower activity of beta 2 is attributed to solvent-exposed isoalloxazine ring in the active site.
- The proposed flavin binding site may also be relevant for the alpha beta enzyme.