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573  structures 5906  species 0  interactions 29176  sequences 380  architectures

Family: Cytochrom_C (PF00034)

Summary: Cytochrome c

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This is the Wikipedia entry entitled "Cytochrome c family". More...

Cytochrome c family Edit Wikipedia article

Cytochrome c
OPM superfamily78
OPM protein1hrc

Cytochromes c (cytC) are electron-transfer proteins having one or several haem c groups, bound to the protein by one or, more generally, two thioether bonds involving sulphydryl groups of cysteine residues. The fifth haem iron ligand is always provided by a histidine residue. Cytochrome c possess a wide range of properties and function in a large number of different redox processes[1].

Ambler[2] recognised four classes of cytC. Class I includes the low-spin soluble cytC of mitochondria and bacteria, with the haem-attachment site towards the N-terminus, and the sixth ligand provided by a methionine residue about 40 residues further on towards the C-terminus. On the basis of sequence similarity, class I cytC were further subdivided into five classes, IA to IE. Class IB includes the eukaryotic mitochondrial cytC and pro karyotic 'short' cyt c2 exemplified by Rhodopila globiformis cyt c2; class IA includes 'long' cyt c2, such as Rhodospirillum rubrum cyt c2 and Aquaspirillum itersonii cyt c-550, which have several extra loops by comparison with class IB cytC.


Human proteins containing this domain



  1. ^ Moore GR, Pettigrew GW (1987). : -. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  2. ^ Ambler RP (1991). "Sequence variability in bacterial cytochromes c". Biochim. Biophys. Acta. 1058 (1): 42–47. PMID 1646017.

This page is based on a Wikipedia article. The text is available under the Creative Commons Attribution/Share-Alike License.

This tab holds the annotation information that is stored in the Pfam database. As we move to using Wikipedia as our main source of annotation, the contents of this tab will be gradually replaced by the Wikipedia tab.

Cytochrome c Provide feedback

The Pfam entry does not include all Prosite members. The cytochrome 556 and cytochrome c' families are not included. All these are now in a new clan together. The C-terminus of DUF989, PF06181 has now been merged into this family.

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External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR009056

After cytochrome c is synthesized in the cytoplasm as apocytochrome c, it is transported through the outer mitochondrial membrane to the intermembrane space, where haem is covalently attached by thioester bonds to two cysteine residues located in the cytochrome c centre. Cytochrome c is required during oxidative phosphorylation as an electron shuttle between Complex III (cytochrome c reductase) and IV (cytochrome c oxidase). In addition, cytochrome c is involved in apoptosis in more complex organisms such as Xenopus, rats and humans. Cellular stress can induce cytochrome c release from the mitochondrial membrane. In mammals, cytochrome c triggers the assembly of the apoptosome, consisting of cytochrome c, Apaf-1 and dATP, which activates caspase-9, leading to cell death [ PUBMED:12729583 , PUBMED:10707095 ]. There are several different members of the cytochrome c family with different functional roles, for instance cytochrome c549 is associated with photosystem II [ PUBMED:11315568 ].

The known structures of c-type cytochromes have six different classes of fold. Of these, four are unique to c-type cytochromes [ PUBMED:12594933 , PUBMED:2166169 ]. The consensus sequence for the cytochrome c centre is Cys-X-X-Cys-His, where the histidine residue is one of the two axial ligands of the haem iron [ PUBMED:10647174 ]. This arrangement is shared by all proteins known to belong to the cytochrome c family, which presently includes both mono-haem proteins and multi-haem proteins. This entry represents mono-haem cytochrome c proteins (excluding class II and f-type cytochromes), such as cytochromes c, c1, c2, c5, c555, c550 to c553, c556, and c6.

Cytochrome c-type centres are also found in the active sites of many enzymes, including cytochrome cd1-nitrite reductase as the N-terminal haem c domain, in quinoprotein alcohol dehydrogenase as the C-terminal domain, in Quinohemoprotein amine dehydrogenase A chain as domains 1 and 2, and in the cytochrome bc1 complex as the cytochrome bc1 domain.

Gene Ontology

The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.

Domain organisation

Below is a listing of the unique domain organisations or architectures in which this domain is found. More...

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Pfam Clan

This family is a member of clan Cytochrome-c (CL0318), which has the following description:

This family includes proteins where a covalently-bound haem completes the core. The core is three helices in an open folded leaf formation. The members are monodomain cytochromes.

The clan contains the following 13 members:

CCP_MauG Cytochrom_C Cytochrom_C1 Cytochrom_C550 Cytochrome-c551 Cytochrome_CBB3 Dehyd-heme_bind DHC DHOR DUF1924 FixO Haem_bd PSCyt1


We store a range of different sequence alignments for families. As well as the seed alignment from which the family is built, we provide the full alignment, generated by searching the sequence database (reference proteomes) using the family HMM. We also generate alignments using four representative proteomes (RP) sets and the UniProtKB sequence database. More...

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We make a range of alignments for each Pfam-A family. You can see a description of each above. You can view these alignments in various ways but please note that some types of alignment are never generated while others may not be available for all families, most commonly because the alignments are too large to handle.

Representative proteomes UniProt
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Representative proteomes UniProt

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We make all of our alignments available in Stockholm format. You can download them here as raw, plain text files or as gzip-compressed files.

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You can also download a FASTA format file containing the full-length sequences for all sequences in the full alignment.

HMM logo

HMM logos is one way of visualising profile HMMs. Logos provide a quick overview of the properties of an HMM in a graphical form. You can see a more detailed description of HMM logos and find out how you can interpret them here. More...


This page displays the phylogenetic tree for this family's seed alignment. We use FastTree to calculate neighbour join trees with a local bootstrap based on 100 resamples (shown next to the tree nodes). FastTree calculates approximately-maximum-likelihood phylogenetic trees from our seed alignment.

Note: You can also download the data file for the tree.

Curation and family details

This section shows the detailed information about the Pfam family. You can see the definitions of many of the terms in this section in the glossary and a fuller explanation of the scoring system that we use in the scores section of the help pages.

Curation View help on the curation process

Seed source: Prosite
Previous IDs: cytochrome_c;
Type: Domain
Sequence Ontology: SO:0000417
Author: Bateman A , Sonnhammer ELL
Number in seed: 53
Number in full: 29176
Average length of the domain: 98.6 aa
Average identity of full alignment: 18 %
Average coverage of the sequence by the domain: 32.57 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 61295632 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 21.3 21.3
Trusted cut-off 21.3 21.3
Noise cut-off 21.2 21.2
Model length: 92
Family (HMM) version: 24
Download: download the raw HMM for this family

Species distribution

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Colour assignments

Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
Viroids Viroids Unclassified sequence Unclassified sequence


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This visualisation provides a simple graphical representation of the distribution of this family across species. You can find the original interactive tree in the adjacent tab. More...

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For those sequences which have a structure in the Protein DataBank, we use the mapping between UniProt, PDB and Pfam coordinate systems from the PDBe group, to allow us to map Pfam domains onto UniProt sequences and three-dimensional protein structures. The table below shows the structures on which the Cytochrom_C domain has been found. There are 573 instances of this domain found in the PDB. Note that there may be multiple copies of the domain in a single PDB structure, since many structures contain multiple copies of the same protein sequence.

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AlphaFold Structure Predictions

The list of proteins below match this family and have AlphaFold predicted structures. Click on the protein accession to view the predicted structure.

Protein Predicted structure External Information
A0A077Z189 View 3D Structure Click here
A0A077ZGY3 View 3D Structure Click here
A0A0D2GYA1 View 3D Structure Click here
A0A0K0ELW4 View 3D Structure Click here
A0A0K0J057 View 3D Structure Click here
A0A0N4U558 View 3D Structure Click here
A0A0P0WGT0 View 3D Structure Click here
A0A0R0GLC2 View 3D Structure Click here
A0A1C1D0H8 View 3D Structure Click here
A0A2K6W0E4 View 3D Structure Click here
A0A3Q0KE61 View 3D Structure Click here
A2Y4S9 View 3D Structure Click here
A4HX28 View 3D Structure Click here
A4HX29 View 3D Structure Click here
A4VND9 View 3D Structure Click here
A8WQY3 View 3D Structure Click here
A8X769 View 3D Structure Click here
B4FYS2 View 3D Structure Click here
B4USV4 View 3D Structure Click here
B6TGS7 View 3D Structure Click here
C0NSH7 View 3D Structure Click here
C0PK55 View 3D Structure Click here
C1H5S3 View 3D Structure Click here
C6SX87 View 3D Structure Click here
C6SYA8 View 3D Structure Click here
C6SZC5 View 3D Structure Click here
C6TJ91 View 3D Structure Click here
D3ZS15 View 3D Structure Click here
D3ZXV2 View 3D Structure Click here
D4A5L9 View 3D Structure Click here
D5ARP7 View 3D Structure Click here
D5WYQ6 View 3D Structure Click here
G3XCY7 View 3D Structure Click here
K0EXG8 View 3D Structure Click here
K7UNJ8 View 3D Structure Click here
O13393 View 3D Structure Click here
O23138 View 3D Structure Click here
O25997 View 3D Structure Click here
O69583 View 3D Structure Click here
P00002 View 3D Structure Click here