Cytochrome P450 2C9 (CYP2C9) is one of the major drug-metabolising proteins in the human liver, metabolising a large range of drugs, e.g. weakly acidic NSAIDs such as ibuprofen. CYP2C9 is localised on the edge of the membrane of the endoplasmic reticulum, to which it is attached via its N-terminal anchor. Its numerous experimental crystal structures lack an N-terminal anchor, as the crystallisation procedure required only a solubilised domain.

Non-selective voltage-gated ion channel that mediates the transport of anions and cations through the mitochondrion outer membrane and plasma membrane (PubMed:8420959). The channel adopts an open conformation at zero mV and a closed conformation at both positive and negative potentials (PubMed:8420959). There are two populations of channels; the main that functions in a lower open-state conductance with lower ion selectivity, that switch, in a voltage-dependent manner, from the open to a low-conducting 'closed' state and the other that has a normal ion selectivity in the typical high conductance, 'open' state (PubMed:8420959). Binds various lipids, including the sphingolipid ceramide, the phospholipid phosphatidylcholine, and the sterols cholesterol and oxysterol (PubMed:31015432). Binding of ceramide promotes the mitochondrial outer membrane permeabilization (MOMP) apoptotic pathway (PubMed:31015432).