1J3S, 3NWV, 3ZCF, 3ZOO, 2N9J, 2N9I5420513063ENSG00000172115ENSMUSG00000063694P99999P62897NM_018947NM_007808NP_061820NP_031834The cytochrome complex, or cyt c, is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion where it plays a critical role in cellular respiration.

It is capable of undergoing oxidation and reduction as its iron atom converts between the ferrous and ferric forms, but does not bind oxygen.

[5][6] Cytochrome c is a highly conserved protein across the spectrum of eukaryotic species, found in plants, animals, fungi, and many unicellular organisms.

Helices α3, α4 and α5 are referred to as 50s, 60s and 70s helices, respectively, when referring to mitochondrial cytochrome c.[15] While most heme proteins are attached to the prosthetic group through iron ion ligation and tertiary interactions, the heme group of cytochrome c makes thioether bonds with two cysteine side chains of the protein.

[16] One of the main properties of heme c, which allows cytochrome c to have variety of functions, is its ability to have different reduction potentials in nature.

[17] The dipole moment has an important role in orienting proteins to the proper directions and enhancing their abilities to bind to other molecules.

[18][19] The dipole moment of cytochrome c results from a cluster of negatively charged amino acid side chains at the "back" of the enzyme.

[21] Cytochrome c binds to cardiolipin in the inner mitochondrial membrane, thus anchoring its presence and keeping it from releasing out of the mitochondria and initiating apoptosis.

[26] Cytochrome c is widely believed to be localised solely in the mitochondrial intermembrane space under normal physiological conditions.

[27] The release of cytochrome c from mitochondria to the cytosol, where it activates the caspase family of proteases, is believed to be the primary trigger leading to the onset of apoptosis.

[28] Measuring the amount of cytochrome c leaking from mitochondria to cytosol, and out of the cell to culture medium, is a sensitive method to monitor the degree of apoptosis.

[32][33][34] This raises the possibility of the existence of yet-unidentified specific mechanisms for protein translocation from mitochondria to other cellular destinations.

[39][40] Inspired from natural examples of enzyme encapsulation in protein-based cage structures (Example: Carboxysomes, Ferritin and Encapsulin), Cytochrome C was encapsulated in a 9 nm small self-assembling DNA binding protein from nutrient starved cells (Dps) protein cage using chimeric self-assembly approach.