Mitochondria 2

Mitochondrial Export

ATP

For every 5 protons pumped into the intermembrane space, 4 are used to drive the ATP synthase and 1 is used to export ATP. In truth, some of the protons provide motive force for a number of transporters for other products that are exchanged (malate, pyruvate, aspartate, etc). The energy also drives the phosphate transporter that exchanges phosphate going in for a hydroxyl ion (OH). The latter then joins with a proton to make water. A parallel ATP/ADP transporter (antiporter) exchanges one ADP going in for and ATP going out.

Hence, the proton motive force used to make ATP is also used for transport and exchange of other products.

Export and production of steroid hormones

Mitochondria work with smooth endoplasmic reticulum to produce final steroid hormones in organs such as adrenal (aldosterone, cortisol, dehydroepiandrosterone); testes (testosterone),, ovary (progesterone or estrogen) or placenta.

Export of cytochrome C and Apoptosis Inducing factor

Mitochondrial products are actively involved in the cascade leading to programmed cell death. Cytochrome C (present in the intermembrane space) is normally sequestered because it is too large to exit via the outer membrane. However, one of the proapoptotic proteins, bax, appears to form and become a part of a channel in the mitochondrial outer membrane. This allows the cytochrome C to escape and become a part of the early events in apoptosis.

Later, a protein bound to the inner membrane (outer surface) called Apoptosis inducing factor. is released as a part of the cascade. The regulators for its release are not well understood.