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0  structures 120  species 0  interactions 249  sequences 8  architectures

Family: SF-assemblin (PF06705)

Summary: SF-assemblin/beta giardin

Pfam includes annotations and additional family information from a range of different sources. These sources can be accessed via the tabs below.

The Pfam group coordinates the annotation of Pfam families in Wikipedia, but we have not yet assigned a Wikipedia article to this family. If you think that a particular Wikipedia article provides good annotation, please let us know.

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.

SF-assemblin/beta giardin Provide feedback

This family consists of several eukaryotic SF-assemblin and related beta giardin proteins. During mitosis the SF-assemblin-based cytoskeleton is reorganised; it divides in prophase and is reduced to two dot-like structures at each spindle pole in metaphase. During anaphase, the two dots present at each pole are connected again. In telophase there is an asymmetrical outgrowth of new fibres. It has been suggested that SF-assemblin is involved in re-establishing the microtubular root system characteristic of interphase cells after mitosis [1].

Literature references

  1. Lechtreck KF, Silflow CD; , Cell Motil Cytoskeleton 1997;36:190-201.: SF-assemblin in Chlamydomonas: sequence conservation and localization during the cell cycle. PUBMED:9015206 EPMC:9015206

  2. Weber K, Geisler N, Plessmann U, Bremerich A, Lechtreck KF, Melkonian M; , J Cell Biol 1993;121:837-845.: SF-assemblin, the structural protein of the 2-nm filaments from striated microtubule associated fibers of algal flagellar roots, forms a segmented coiled coil. PUBMED:8491776 EPMC:8491776

Internal database links

This tab holds annotation information from the InterPro database.

InterPro entry IPR008374

Striated fibre assemblin (SFA), an acidic 33kDa protein, is the major component of striated microtubule-associated fibres (SMAFs) in the flagellar basal apparatus of green flagellates. In Chlamydomonas, and other green flagellates, the SMAFs form a cross-like pattern and run alongside the proximal parts of four bundles of flagellar root microtubules.

The sequence of SFA contains two structurally distinct domains [ PUBMED:8491776 ]. The head domain, with ~30 residues, contains all the prolines (3-8 depending on species) and is rich in hydroxyamino acids. This non-helical domain is further characterised by the presence of repetitive SP-motifs, some of them in the context SP(M/T)R, which is a putative substrate for p34-CDC2 kinase. The rod domain, with ~250 residues, is predicted to be mostly alpha- helical (the alpha-helix content was estimated to be 76% for the entire molecule or 85% for the postulated rod domain). This domain shows a pronounced coiled-coil-forming ability and contains a 29-residue repeat pattern based on four heptads, followed by a skip residue. The rod domains of SF-assemblin and beta-giardin from protozoan Giardia have the same length and display 42% sequence similarity [ PUBMED:8491776 , PUBMED:19214572 ].

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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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: Pfam-B_22934 (release 10.0)
Previous IDs: none
Type: Family
Sequence Ontology: SO:0100021
Author: Moxon SJ
Number in seed: 3
Number in full: 249
Average length of the domain: 215.8 aa
Average identity of full alignment: 21 %
Average coverage of the sequence by the domain: 67.35 %

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 30.6 30.6
Trusted cut-off 30.6 30.7
Noise cut-off 30.2 30.5
Model length: 247
Family (HMM) version: 14
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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The tree shows the occurrence of this domain across different species. More...


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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
Q8IAN2 View 3D Structure Click here
Q8ILD3 View 3D Structure Click here

trRosetta Structure

The structural model below was generated by the Baker group with the trRosetta software using the Pfam UniProt multiple sequence alignment.

The InterPro website shows the contact map for the Pfam SEED alignment. Hovering or clicking on a contact position will highlight its connection to other residues in the alignment, as well as on the 3D structure.

Improved protein structure prediction using predicted inter-residue orientations. Jianyi Yang, Ivan Anishchenko, Hahnbeom Park, Zhenling Peng, Sergey Ovchinnikov, David Baker Proceedings of the National Academy of Sciences Jan 2020, 117 (3) 1496-1503; DOI: 10.1073/pnas.1914677117;