intermembranaire

Intermembranaire is a term used in cell biology to describe the space between two adjacent membranes. It is most often applied to the intermembrane space of mitochondria, the compartment located between the outer mitochondrial membrane and the inner mitochondrial membrane. The concept can also refer to similar spaces in other double-membrane organelles, but the mitochondrial usage is by far the most common.

In mitochondria, the intermembrane space is a narrow compartment that harbors a specific set of ions, small molecules, and proteins. The inner membrane separates the matrix from the intermembrane space, while the outer membrane contains channels that allow metabolites to diffuse into the space. The accumulation of protons in this region, pumped across the inner membrane by the respiratory chain, helps generate the proton motive force used to drive ATP synthesis.

Functionally, the intermembrane space is integral to energy production and apoptosis. Protons pumped into this space contribute to the electrochemical gradient exploited by ATP synthase to produce ATP. The space also serves as a reservoir for cytochrome c and other proteins that can be released into the cytosol in response to cellular stress, triggering caspase activation and programmed cell death.

Protein targeting and maturation in the intermembrane space involve specialized import and folding mechanisms, such as the Mia40/Erv1 pathway, which help maintain the proper set of IMS proteins. Dysregulation of IMS composition or permeability can impact mitochondrial function and cell fate.