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17  structures 184  species 0  interactions 272  sequences 6  architectures

Family: PetG (PF02529)

Summary: Cytochrome B6-F complex subunit 5

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Cytochrome B6-F complex subunit 5 Provide feedback

This family consists of cytochrome B6-F complex subunit 5 (PetG). The cytochrome bf complex found in green plants, eukaryotic algae and cyanobacteria, connects photosystem I to photosystem II in the electron transport chain, functioning as a plastoquinol:plastocyanin c6 oxidoreductase [1]. PetG or subunit 5 is associated with the bf complex and the absence of PetG affects either the assembly or stability of the cytochrome bf complex in Chlamydomonas reinhardtii [1].

Literature references

  1. Berthold DA, Schmidt CL, Malkin R; , J Biol Chem 1995;270:29293-29298.: The deletion of petG in Chlamydomonas reinhardtii disrupts the cytochrome bf complex. PUBMED:7493961 EPMC:7493961

  2. Pierre Y, Breyton C, Kramer D, Popot JL; , J Biol Chem 1995;270:29342-29349.: Purification and characterization of the cytochrome b6 f complex from Chlamydomonas reinhardtii. PUBMED:7493968 EPMC:7493968

This tab holds annotation information from the InterPro database.

InterPro entry IPR003683

This family consists of cytochrome b6/f complex subunit 5 (PetG). The cytochrome bf complex, found in green plants, eukaryotic algae and cyanobacteria, connects photosystem I to photosystem II in the electron transport chain, functioning as a plastoquinol:plastocyanin/cytochrome c6 oxidoreductase [ PUBMED:7493961 ]. The purified complex from the unicellular alga Chlamydomonas reinhardtii contains seven subunits; namely four high molecular weight subunits (cytochrome f, Rieske iron-sulphur protein, cytochrome b6, and subunit IV) and three approximately miniproteins (PetG, PetL, and PetX) [ PUBMED:7493968 ]. Stoichiometry measurements are consistent with every subunit being present as two copies per b6/f dimer. The absence of PetG affects either the assembly or stability of the cytochrome bf complex in C. reinhardtii [ PUBMED:7493961 ].

Gene Ontology

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Domain organisation

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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.

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Representative proteomes UniProt

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

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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.

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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_1348 (release 5.4)
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Bashton M , Bateman A
Number in seed: 14
Number in full: 272
Average length of the domain: 35.50 aa
Average identity of full alignment: 72 %
Average coverage of the sequence by the domain: 68.30 %

HMM information View help on HMM parameters

HMM build commands:
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
Model details:
Parameter Sequence Domain
Gathering cut-off 23.7 23.7
Trusted cut-off 24.3 40.7
Noise cut-off 22.2 23.6
Model length: 36
Family (HMM) version: 17
Download: download the raw HMM for this family

Species distribution

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Archea Archea Eukaryota Eukaryota
Bacteria Bacteria Other sequences Other sequences
Viruses Viruses Unclassified Unclassified
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 PetG domain has been found. There are 17 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
A0A0R0G5A8 View 3D Structure Click here
P0C392 View 3D Structure Click here
P56775 View 3D Structure Click here
P69457 View 3D Structure Click here
Q2PMR5 View 3D Structure Click here