Summary: IQ calmodulin-binding motif
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This is the Wikipedia entry entitled "IQ calmodulin-binding motif". More...
IQ calmodulin-binding motif Edit Wikipedia article
| IQ calmodulin-binding motif | |||||||||||
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 Structure of the regulatory domain of scallop myosin at 2 A resolution.[1] | |||||||||||
| Identifiers | |||||||||||
| Symbol | IQ | ||||||||||
| Pfam | PF00612 | ||||||||||
| InterPro | IPR000048 | ||||||||||
| SMART | SM00015 | ||||||||||
| PROSITE | PS50096 | ||||||||||
| SCOPe | 1wdc / SUPFAM | ||||||||||
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The IQ calmodulin-binding motif is an amino acid sequence motif containing the following sequence:
- [FILV]Qxxx[RK]Gxxx[RK]xx[FILVWY]
The term "IQ" refers to the first two amino acids of the motif: isoleucine (commonly) and glutamine (invariably).
Function
Calmodulin (CaM) is recognized as a major calcium (Ca2+) sensor and orchestrator of regulatory events through its interaction with a diverse group of cellular proteins. Three classes of recognition motifs exist for many of the known CaM binding proteins; the IQ motif as a consensus for Ca2+-independent binding and two related motifs for Ca2+-dependent binding, termed 1-14 and 1-5-10 based on the position of conserved hydrophobic residues.[2]
Example
The regulatory domain of scallop myosin is a three-chain protein complex that switches on this motor in response to Ca2+ binding. Side-chain interactions link the two light chains in tandem to adjacent segments of the heavy chain bearing the IQ-sequence motif. The Ca2+-binding site is a novel EF hand motif on the essential light chain and is stabilized by linkages involving the heavy chain and both light chains, accounting for the requirement of all three chains for Ca2+binding and regulation in the intact myosin molecule.[3]
References
- ^ Houdusse A, Cohen C (January 1996). "Structure of the regulatory domain of scallop myosin at 2 A resolution: implications for regulation". Structure. 4 (1): 21–32. doi:10.1016/S0969-2126(96)00006-8. PMID 8805510.
- ^ Rhoads AR, Friedberg F (April 1997). "Sequence motifs for calmodulin recognition". FASEB J. 11 (5): 331–40. doi:10.1096/fasebj.11.5.9141499. PMID 9141499.
- ^ Xie X, Harrison DH, Schlichting I, Sweet RM, Kalabokis VN, Szent-Györgyi AG, Cohen C (March 1994). "Structure of the regulatory domain of scallop myosin at 2.8 A resolution". Nature. 368 (6469): 306–12. doi:10.1038/368306a0. PMID 8127365.
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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.
IQ calmodulin-binding motif Provide feedback
Calmodulin-binding motif.
Literature references
-
Xie X, Harrison DH, Schlichting I, Sweet RM, Kalabokis VN, Szent-Gyorgyi AG, Cohen C; , Nature 1994;368:306-312.: Structure of the regulatory domain of scallop myosin at 2.8 A resolution. PUBMED:8127365 EPMC:8127365
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Rhoads AR, Friedberg F; , FASEB J 1997;11:331-340.: Sequence motifs for calmodulin recognition. PUBMED:9141499 EPMC:9141499
Internal database links
| SCOOP: | BAG Myosin_tail_1 |
External database links
| HOMSTRAD: | MYSc |
| SCOP: | 1wdc |
| SMART: | IQ |
This tab holds annotation information from the InterPro database.
InterPro entry IPR000048
The IQ motif is an extremely basic unit of about 23 amino acids, whose conserved core usually fits the consensus A-x(3)-I-Q-x(2)-F-R-x(4)-K-K. The IQ motif, which can be present in one or more copies, serves as a binding site for different EF-hand proteins including the essential and regulatory myosin light chains, calmodulin (CaM), and CaM-like proteins [ PUBMED:1558751 , PUBMED:9141499 ].Many IQ motifs are protein kinase C (PKC) phosphorylation sites [ PUBMED:1824695 , PUBMED:8424932 ].
Resolution of the 3D structure of scallop myosin has shown that the IQ motif forms a basic amphipathic helix [ PUBMED:8127365 ].
Some proteins known to contain an IQ motif are listed below:
- A number of conventional and unconventional myosins.
- Neuromodulin (GAP-43). This protein is associated with nerve growth. It is a major component of the motile "growth cones" that form the tips of elongating axons.
- Neurogranin (NG/p17). Acts as a "third messenger" substrate of protein kinase C-mediated molecular cascades during synaptic development and remodeling.
- Sperm surface protein Sp17.
- Ras GTPase-activating-like protein IQGAP1. IQGAP1 contains 4 IQ motifs.
This entry covers the entire IQ motif.
Gene Ontology
The mapping between Pfam and Gene Ontology is provided by InterPro. If you use this data please cite InterPro.
| Molecular function | protein binding (GO:0005515) |
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 EF_hand (CL0220), which has the following description:
The EF hand is a calcium binding domain found in a wide variety of proteins [1].
The clan contains the following 31 members:
Ca_chan_IQ Caleosin Cbl_N2 Cullin_binding DAG_kinase_N Dockerin_1 EF-hand_1 EF-hand_10 EF-hand_11 EF-hand_12 EF-hand_13 EF-hand_14 EF-hand_2 EF-hand_3 EF-hand_4 EF-hand_5 EF-hand_6 EF-hand_7 EF-hand_8 EF-hand_9 EF-hand_like EF_assoc_2 EFhand_Ca_insen Internalin_N IQ IQCJ-SCHIP1 NADPH_Ox p25-alpha S_100 SPARC_Ca_bdg WEF-handAlignments
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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| Seed (245) |
Full (82891) |
Representative proteomes | UniProt (151320) |
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| RP15 (11929) |
RP35 (34195) |
RP55 (67459) |
RP75 (91969) |
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| HTML | |||||||
| PP/heatmap | 1 | ||||||
1Cannot generate PP/Heatmap alignments for seeds; no PP data available
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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.
| Seed (245) |
Full (82891) |
Representative proteomes | UniProt (151320) |
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|---|---|---|---|---|---|---|---|
| RP15 (11929) |
RP35 (34195) |
RP55 (67459) |
RP75 (91969) |
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| Raw Stockholm | |||||||
| Gzipped | |||||||
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...
Trees
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
| Seed source: | SMART |
| Previous IDs: | none |
| Type: | Motif |
| Sequence Ontology: | SO:0001067 |
| Author: |
Ponting CP  , Schultz J, Bork P
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| Number in seed: | 245 |
| Number in full: | 82891 |
| Average length of the domain: | 20.60 aa |
| Average identity of full alignment: | 33 % |
| Average coverage of the sequence by the domain: | 4.54 % |
HMM information
| HMM build commands: |
build method: hmmbuild -o /dev/null HMM SEED
search method: hmmsearch -Z 57096847 -E 1000 --cpu 4 HMM pfamseq
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| Model details: |
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| Model length: | 21 | ||||||||||||
| Family (HMM) version: | 29 | ||||||||||||
| Download: | download the raw HMM for this family |
Species distribution
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Structures
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 IQ domain has been found. There are 60 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.
