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Spontaneous subunit exchange in porcine liver fructose-1,6-bisphosphatase
S W Nelson1, R B Honzatko, H J Fromm
1Department of Biochemistry, Biophysics, and Molecular Biology, 1210 Molecular Biology Bldg., Iowa State University, Ames, IA 50011, USA.
FEBS Letters
|March 21, 2001
Summary
Mammalian fructose-1,6-bisphosphatase tetramers can exchange subunits, challenging previous assumptions. This subunit exchange is influenced by ligands and may impact enzyme regulation.
Area of Science:
- Biochemistry
- Enzymology
- Protein dynamics
Background:
- Mammalian fructose-1,6-bisphosphatase (FBPase) is a key metabolic enzyme.
- Tetrameric structure of FBPase was previously thought to be stable, with no subunit exchange.
Purpose of the Study:
- To investigate the potential for subunit exchange in mammalian FBPase tetramers.
- To understand how ligands affect FBPase subunit dynamics and allosteric regulation.
Main Methods:
- Engineering a mutant FBPase with altered electrostatic charge on its subunits.
- Monitoring subunit exchange using non-denaturing gel electrophoresis and anion exchange chromatography.
- Assessing the impact of active site ligands (fructose 6-phosphate) and allosteric regulators (AMP) on exchange.
Main Results:
- Engineered FBPase with altered charge spontaneously exchanges subunits with wild-type enzyme.
- Subunit exchange reaches equilibrium within 5 hours at 4°C.
- Active site ligands inhibit monomer exchange but allow dimer exchange; AMP abolishes all exchange.
Conclusions:
- Subunit exchange is a possible phenomenon in mammalian FBPase tetramers.
- Ligand binding significantly modulates the extent and type of subunit exchange.
- These exchange dynamics may be integral to the allosteric regulatory mechanism of FBPase.