Affixing N-terminal α-helix to the wall of the voltage-dependent anion channel does not prevent its voltage gating.

The voltage-dependent anion channel (VDAC) governs the free exchange of ions and metabolites between the mitochondria and the rest of the cell. The three-dimensional structure of VDAC1 reveals a channel formed by 19 β-strands and an N-terminal α-helix located near the midpoint of the pore. The position of this α-helix causes a narrowing of the cavity, but ample space for metabolite passage remains.

High-throughput crystallization of membrane proteins using the lipidic bicelle method.

Membrane proteins (MPs) play a critical role in many physiological processes such as pumping specific molecules across the otherwise impermeable membrane bilayer that surrounds all cells and organelles. Alterations in the function of MPs result in many human diseases and disorders; thus, an intricate understanding of their structures remains a critical objective for biological research. However, structure determination of MPs remains a significant challenge often stemming from their hydrophobicity.

Crystallizing membrane proteins using lipidic bicelles.

Crystallization of membrane proteins remains a significant challenge. For proteins resistant to the traditional approach of directly crystallizing from detergents, lipidic phase crystallization can be a powerful tool. Bicelles are an excellent medium for crystallizing membrane proteins in a lipidic environment.

Fluorescence Detection of Heavy Atom Labeling (FD-HAL): a rapid method for identifying covalently modified cysteine residues by phasing atoms.

Membrane protein crystallography frequently stalls at the phase determination stage due to poor crystal diffraction and the inability to identify heavy atom derivatization prior to data collection. Thus, a majority of time, effort and resources are invested preparing potential derivatized crystals for synchrotron data collection and analysis without knowledge of heavy atom labeling. To remove this uncertainty, we introduce Fluorescence Detection of Heavy Atom Labeling (FD-HAL) using tetramethylrhodamine-5-maleimide (a fluorescent maleimide compound) to monitor in-gel cysteine residue accessibility and ascertain covalent modification by mercury, platinum and gold compounds.

Post-translational modifications of integral membrane proteins resolved by top-down Fourier transform mass spectrometry with collisionally activated dissociation.

Integral membrane proteins remain a challenge to proteomics because they contain domains with physicochemical properties poorly suited to today's bottom-up protocols. These transmembrane regions may potentially contain post-translational modifications of functional significance, and thus development of protocols for improved coverage in these domains is important. One way to achieve this goal is by using top-down mass spectrometry whereby the intact protein is subjected to mass spectrometry and dissociation.

The electrostatics of VDAC: implications for selectivity and gating.

The voltage-dependent anion channel (VDAC) is the major pathway mediating the transfer of metabolites and ions across the mitochondrial outer membrane. Two hallmarks of the channel in the open state are high metabolite flux and anion selectivity, while the partially closed state blocks metabolites and is cation selective. Here we report the results from electrostatics calculations carried out on the recently determined high-resolution structure of murine VDAC1 (mVDAC1).

Crystal packing analysis of murine VDAC1 crystals in a lipidic environment reveals novel insights on oligomerization and orientation.

All eukaryotic cells require efficient trafficking of metabolites between the mitochondria and the rest of the cell. This exchange is carried out by the dominant protein in the outer mitochondrial membrane (OMM), the Voltage Dependent Anion Channel (VDAC), which serves as the primary pathway for the exchange of ions and metabolites between the cytoplasm and the intermembrane space of the mitochondria. Additionally, VDAC provides a scaffold for the binding of modulator proteins to the mitochondria and has been implicated in mitochondria-dependent cell death.

The crystal structure of mouse VDAC1 at 2.3 A resolution reveals mechanistic insights into metabolite gating.

The voltage-dependent anion channel (VDAC) constitutes the major pathway for the entry and exit of metabolites across the outer membrane of the mitochondria and can serve as a scaffold for molecules that modulate the organelle. We report the crystal structure of a beta-barrel eukaryotic membrane protein, the murine VDAC1 (mVDAC1) at 2.3 A resolution, revealing a high-resolution image of its architecture formed by 19 beta-strands.