CYCS
Цитохром цис - белок, который кодируется геном CYCS. Белок-носитель электронов. Окисленная форма может принимать электрон из гемовой группы из субъединицы цитохрома С1 цитохромредуктазы. Затем цитохром С переносит этот электрон в комплекс цитохромоксидазы, конечный белковый носитель в митохондриальной цепи переноса электронов.
Cytochrome c (Cytc) is a water-soluble protein in humans that is encoded by the CYCS gene. Cytochrome c is initially synthesized as an apocytochrome c lacking heme in the cytoplasm. The heme prosthetic group is covalently ligated to the apocytochrome c peptide chain via two (or very rarely one) thioether linkages between the vinyl groups of heme and two cysteines sulfhydryls of a conserved CysXxxXxxCysHis (CXXCH) heme-binding motif. The reaction is catalyzed by cytochrome c heme lyase (CCHL). The addition of heme to an apocytochrome c is a requirement for cytochrome c import into mitochondria. Mature cytochrome c is located in the mitochondrial intermembrane space (IMS) and loosely attached to the surface of the inner mitochondrial membrane. Cytochrome c is functionally involved in the electron transport chain (ETC) of mitochondria. Electron transport is part of the pathway for the synthesis of ATP. The oxidized form of the cytochrome c heme group can accept an electron from the heme group of the cytochrome c1 subunit of cytochrome reductase. Cytochrome c and then transfers this electron to the cytochrome oxidase complex, and the final protein carrier in the mitochondrial electron-transport chain. Cytc is essential for aerobic energy production, and cytochrome c-null mice died around midgestation. In addition to its role in mitochondrial respiration, cytochrome c plays a crucial role in apoptotic signaling. Cytochrome c is a pivotal protein that initiates the intrinsic apoptosis pathway. Stimulated by apoptotic signals, mitochondrial outer membrane permeability (MOMP) is enhanced, leading to the release of cytochrome c into the cytosol. Free cytochrome c binds to apoptotic protease-activating factor 1 (Apaf-1), forming an apoptosome that then switches on caspases. These enzymes chew up cellular proteins, inducing apoptosis. The release of cytochrome c and cytochrome-c-mediated apoptosis are prominently controlled and regulated by the members of the B-cell lymphoma protein-2 (BCL2) family. Interestingly, cytochrome c itself undergoes antiapoptotic modification by glucose metabolism. Allyson E. Vaughn and Mohanish Deshmuk showed that NADPH derived from the pentose phosphate pathway controls redox state of cytochrome c and indicated that glucose metabolism negatively regulates apoptosis even downstream of MOMP through the production of NADPH. Recent discoveries of additional functions of cytochrome c, including its activity as a cardiolipin peroxidase and the detection of four phosphorylation sites on cytochrome c, suggest that its multiple functions are regulated by cell signaling pathways. |
