The Mitochondrial Permeability Transition Pore: Past, Present, and Future

Area of Science:

• Mitochondrial physiology and bioenergetics
• Molecular biology of ion channels
• Comparative biochemistry

Background:

• The mitochondrial permeability transition (PT) is a critical event involving increased inner mitochondrial membrane permeability.
• This process is mediated by the opening of the permeability transition pore (PTP), a high-conductance channel.
• While the molecular identity of the PTP has been debated, consensus points to specific conformations of F_OF₁-ATP synthase and the adenine nucleotide translocator.

Purpose of the Study:

• To investigate the role of ATP synthase in forming channels related to mitochondrial permeability transition.
• To compare the channel-forming properties of ATP synthases across different species with varying PT susceptibility.
• To provide a structural framework for understanding the mechanism of channel formation or its absence.

Main Methods:

• Comparative analysis of ATP synthase structures from various species.
• Review of existing literature on mitochondrial permeability transition and channel formation.
• Inferences drawn from structural data to hypothesize about channel mechanisms.

Main Results:

• ATP synthase forms high-conductance channels in mammals and yeast, associated with PT.
• ATP synthase in *Artemia franciscana* does not form high-conductance channels and is refractory to PT.
• ATP synthase in *Drosophila melanogaster* forms low-conductance, Ca2+-selective channels, leading to Ca2+-induced Ca2+ release but not PT.

Conclusions:

• The channel-forming capacity of ATP synthase varies significantly across species.
• Species-specific structural differences in ATP synthase likely determine their susceptibility to mitochondrial permeability transition.
• Structural insights into ATP synthases offer a testable model for future research on PTP mechanisms.