Sandbox Reserved 1626: Difference between revisions

The mitochondrial calcium unipoter (MCU) denotes the channel protein itself, not to be confused with the MCU complex. The MCU was originally thought to be composed of a [https://en.wikipedia.org/wiki/Pentamer pentamer] of five identical subunits, but it is now known to exist as a [https://en.wikipedia.org/wiki/Dimer_(chemistry) dimer] of <scene name='83/832952/Dimer_of_dimers/5'>dimers</scene>.<ref name="Woods">PMID:31869674</ref> The protein as a whole is composed of a [https://en.wikipedia.org/wiki/Coiled_coil coiled-coil] domain, a transmembrane domain, and a non-translated domain.<ref name="Woods"/> The hydrophobic <scene name='83/832952/New_ones/3'>transmembrane domain</scene> is located in the inner mitochondrial membrane ([https://en.wikipedia.org/wiki/Inner_mitochondrial_membrane IMM]) and the hydrophilic coiled-coil domain exists in the mitochondrial matrix.<ref name="Baradaran"/> The transmembrane domain (TMD) consists of eight separate helices (TM1 and TM2 from each subunit) that are connected by mostly hydrophobic amino acids in the IMS and has four-fold symmetry.<ref name="Baradaran"/>  <scene name='83/832952/Tm1/2'>TM1</scene> packs tightly against <scene name='83/832952/Tm2/2'>TM2</scene> from the neighboring subunit which conveys a sense of domain-swapping.<ref name="Fan">PMID:29995856</ref> This section of the MCU can be roughly divided into a narrow outer leaflet portion with the selectivity filter and lined by the <scene name='83/832952/Tm2/2'>TM2</scene> helices and a wide inner leaflet.<ref name="Baradaran"/> Past the transmembrane domain, the N-terminal domains of the <scene name='83/832952/Tm1/2'>TM1</scene> helices extend into the matrix and form coiled-coils with a C-terminal helix.<ref name="Baradaran"/> These "legs" are separated from each other which allows enough space for calcium ions to diffuse out into the matrix.<ref name="Baradaran"/> Additionally, this domain is responsible for assembly of the MCU and [https://en.wikipedia.org/wiki/Post-translational_modification post-translational modification].<ref name="Fan"/> Finally, each leg ends in a <scene name='83/832952/New_ones/4'>non-translated domain</scene> (NTD).<ref name="Baradaran"/> While the MCU can intake calcium without the NTD, it may have regulatory functions and the ability to bend transmembrane helices to constrict the pore.<ref name="Baradaran"/> <ref name="Fan"/>