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6  structures 780  species 0  interactions 2793  sequences 74  architectures

Family: Cytochrom_B561 (PF03188)

Summary: Eukaryotic cytochrome b561

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This is the Wikipedia entry entitled "Cytochrome b561". More...

Cytochrome b561 Edit Wikipedia article

Eukaryotic cytochrome b561
Symbol Cytochrom_B561
Pfam PF03188
Pfam clan CL0328
InterPro IPR004877
TCDB 5.B.2.
CDD cd08554
Prokaryotic cytochrome b561
Symbol Ni_hydr_CYTB
Pfam PF01292
Pfam clan CL0328
InterPro IPR011577
OPM superfamily 3
OPM protein 4gd3

Cytochrome b561 is an integral membrane protein responsible for electron transport, binding two heme groups non-covalently.[1] It is a family of ascorbate-dependent oxidoreductase enzymes.[2]

Human proteins containing this domain


  1. ^ Cytochrome b561, Uniprot
  2. ^ Lu, P.; Ma, D.; Yan, C.; Gong, X.; Du, M.; Shi, Y. (21 January 2014). "Structure and mechanism of a eukaryotic transmembrane ascorbate-dependent oxidoreductase". Proceedings of the National Academy of Sciences 111 (5): 1813–1818. doi:10.1073/pnas.1323931111. 

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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.

Eukaryotic cytochrome b561 Provide feedback

Cytochrome b561 is a secretory vesicle-specific electron transport protein. It is an integral membrane protein, that binds two heme groups non-covalently. This is a eukaryotic family. Members of the 'prokaryotic cytochrome b561' family can be found in Pfam: PF01292.

Literature references

  1. Okuyama E, Yamamoto R, Ichikawa Y, Tsubaki M; , Biochim Biophys Acta. 1998;1383:269-278.: Structural basis for the electron transfer across the chromaffin vesicle membranes catalyzed by cytochrome b561: analyses of cDNA nucleotide sequences and visible absorption spectra. PUBMED:9602148 EPMC:9602148

Internal database links

External database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR004877

Cytochrome b561 is a secretory vesicle-specific electron transport protein [PUBMED:9602148]. It is an integral membrane protein, that binds two haem groups non-covalently. This entry represents the eukaryotic family. Members of the 'bacterial cytochrome b561' family can be found in INTERPRO.

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 2heme_cytochrom (CL0328), which has the following description:

This superfamily includes a variety of different heme binding cytochromes.

The clan contains the following 9 members:

COX15-CtaA Cytochrom_B561 Cytochrom_B_N_2 Cytochrom_C_asm Cytochrome_B DUF2427 DUF4405 Ferric_reduct Ni_hydr_CYTB


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 using the family HMM. We also generate alignments using four representative proteomes (RP) sets, the NCBI sequence database, and our metagenomics sequence database. More...

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

External links

MyHits provides a collection of tools to handle multiple sequence alignments. For example, one can refine a seed alignment (sequence addition or removal, re-alignment or manual edition) and then search databases for remote homologs using HMMER3.

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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: Pfam-B_2927 (release 6.5) & Pfam-B_7165 (Release 8.0)
Previous IDs: Cytochrome_B561;
Type: Family
Author: Mifsud W
Number in seed: 39
Number in full: 2793
Average length of the domain: 130.10 aa
Average identity of full alignment: 21 %
Average coverage of the sequence by the domain: 40.38 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 80369284 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 21.1 21.1
Trusted cut-off 21.1 21.1
Noise cut-off 21.0 21.0
Model length: 137
Family (HMM) version: 12
Download: download the raw HMM for this family

Species distribution

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Archea Archea Eukaryota Eukaryota
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Viroids Viroids Unclassified sequence Unclassified sequence


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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_B561 domain has been found. There are 6 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 seqence.

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