N-helix and Cysteines Inter-regulate Human Mitochondrial VDAC-2 Function and Biochemistry.
Svetlana Rajkumar Maurya1, Radhakrishnan Mahalakshmi2
1From the Department of Biological Sciences, Molecular Biophysics Laboratory, Indian Institute of Science Education and Research, Bhopal 462023, India.
The Journal of Biological Chemistry
|October 22, 2015
Summary
Human voltage-dependent anion channel-2 (hVDAC-2) has a unique N-terminal extension (NTE) that influences its refolding and stability. This NTE also sensitizes hVDAC-2 to voltage gating, differentiating it from other VDACs.
Area of Science:
- Biophysics
- Molecular Biology
- Biochemistry
Background:
- Human voltage-dependent anion channel-2 (hVDAC-2) is an anti-apoptotic protein in the outer mitochondrial membrane and a metabolite transporter.
- hVDAC-2 uniquely possesses an 11-residue extension (NTE) on its N-terminal helix (NTH).
Purpose of the Study:
- To elucidate the specific role of the NTE in hVDAC-2's function, stability, and gating properties.
- To investigate the interplay between the NTH, NTE, and cysteine residues in hVDAC-2's channel activity and stability.
Main Methods:
- Electrophysiology to assess channel activity and voltage gating.
- Biochemical assays to determine refolding kinetics and thermodynamic stability.
- Analysis of hVDAC-2's cysteine content and its functional implications.
Main Results:
- The NTH is essential for channel activity, while the NTE modulates voltage sensitivity.
- The NTE influences chaperone-independent refolding and thermodynamic stability of hVDAC-2.
- Interdependent roles of the NTH and cysteines in channel function and stability were identified.
Conclusions:
- The NTE plays a critical role in the unique functional and stability characteristics of hVDAC-2.
- Cysteine residues contribute to regulating reactive oxygen species and channel function.
- These findings highlight evolutionary factors that distinguish hVDAC-2 from other VDAC isoforms.
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