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Modeling Ligands into Maps Derived from Electron Cryomicroscopy
Published on: July 19, 2024
Crystal structure of unliganded TRAP: implications for dynamic allostery
Ali D Malay1, Masahiro Watanabe, Jonathan G Heddle
1Heddle Initiative Research Unit, RIKEN,Wako, Saitama 351-0198, Japan.
The Biochemical Journal
|December 24, 2010
Summary
Tryptophan-bound TRAP (trp RNA-binding attenuation protein) usually binds RNA. However, low temperatures allow unbound TRAP to bind RNA, suggesting dynamic, not structural, changes regulate this process.
Area of Science:
- Biochemistry
- Molecular Biology
- Structural Biology
Background:
- Allosteric regulation is crucial for protein function, often involving ligand binding.
- Protein dynamics, rather than just conformational changes, can mediate communication between distant binding sites.
- TRAP (trp RNA-binding attenuation protein) regulates the trp operon in Bacillus species via tryptophan binding to mRNA.
Purpose of the Study:
- To investigate the mechanism of TRAP-RNA interaction.
- To explore the role of protein dynamics versus structural changes in TRAP allostery.
- To characterize TRAP binding to RNA in the absence of tryptophan, particularly at low temperatures.
Main Methods:
- Crystal structure determination of apo-TRAP (tryptophan-unbound form).
- Biochemical assays to assess TRAP-RNA binding affinity at varying temperatures and tryptophan concentrations.
- Comparative analysis of apo-TRAP and holo-TRAP structures.
Main Results:
- Contrary to expectations, TRAP binds RNA at low temperatures even without tryptophan.
- The crystal structure of apo-TRAP shows minimal deviation from the tryptophan-bound form.
- Bacillus stearothermophilus TRAP exhibits a particularly strong low-temperature RNA binding effect in the absence of tryptophan.
Conclusions:
- Tryptophan's effect on TRAP-RNA binding is likely mediated by dynamic changes, not static structural alterations.
- Low temperatures can mimic the allosteric effect of tryptophan binding on TRAP.
- Protein dynamics play a significant role in the allosteric regulation of TRAP function.
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