The domain within your query sequence starts at position 2041 and ends at position 2132; the E-value for the IG_FLMN domain shown below is 1.52e-41.

DASKVRVWGKGLSEGQTFQVAEFIVDTRNAGYGGLGLSIEGPSKVDINCEDMEDGTCKVT
YCPTEPGTYIINIKFADKHVPGSPFTVKVTGE

IG_FLMN

Filamin-type immunoglobulin domains

• SMART accession number: SM00557
• Description: These form a rod-like structure in the actin-binding cytoskeleton protein, filamin. The C-terminal repeats of filamin bind beta1-integrin (CD29).
• Interpro abstract (IPR001298):

  The many different actin cross-linking proteins share a common architecture, consisting of a globular actin-binding domain and an extended rod. Whereas their actin-binding domains consist of two calponin homology domains (see IPR001715 ), their rods fall into three families.

  The rod domain of the family including the Dictyostelium discoideum (Slime mould) gelation factor (ABP120) and human filamin (ABP280) is constructed from tandem repeats of a 100-residue motif that is glycine and proline rich [ (PUBMED:9164464) ]. The gelation factor's rod contains 6 copies of the repeat, whereas filamin has a rod constructed from 24 repeats. The resolution of the 3D structure of rod repeats from the gelation factor has shown that they consist of a beta-sandwich, formed by two beta-sheets arranged in an immunoglobulin-like fold [ (PUBMED:9164464) (PUBMED:10467095) ]. Because conserved residues that form the core of the repeats are preserved in filamin, the repeat structure should be common to the members of the gelation factor/filamin family.

  The head to tail homodimerisation is crucial to the function of the ABP120 and ABP280 proteins. This interaction involves a small portion at the distal end of the rod domains. For the gelation factor it has been shown that the carboxy-terminal repeat 6 dimerises through a double edge-to-edge extension of the beta-sheet and that repeat 5 contributes to dimerisation to some extent [ (PUBMED:9417983) (PUBMED:10467095) (PUBMED:2668299) ].

• GO function: protein binding (GO:0005515)

There are 64366 IG_FLMN domains in 8225 proteins in SMART's nrdb database.

Literature (relevant references for this domain)

Primary literature is listed below; Automatically-derived, secondary literature is also avaliable.

• Fucini P et al.
• Molecular architecture of the rod domain of the Dictyostelium gelation factor (ABP120).
• J Mol Biol. 1999; 291: 1017-23

The Dictyostelium discoideum gelation factor is a two-chain actin-cross-linking protein that, in addition to an N-terminal actin-binding domain, has a rod domain constructed from six tandem repeats of a 100-residue motif that has an immunoglobulin fold. To define the architecture of the rod domain of gelation factor, we have expressed in E. coli a series of constructs corresponding to different numbers of gelation factor rod repeats and have characterised them by chemical crosslinking, ultracentrifugation, column chromatography, matrix-assisted laser desorption ionisation (MALDI) mass spectrometry and NMR spectroscopy. Fragments corresponding to repeats 1-6 and 5-6 dimerise, whereas repeats 1-5 and single repeats 3 and 4 are monomeric. Repeat 6 interacts weakly and was present as monomer and dimer when analysed by analytical ultracentrifugation. Proteolytic digestion of rod5-6 resulted in the generation of two polypeptides that roughly corresponded to rod5 and part of rod6. None of these polypeptides formed dimers after chemical crosslinking. Stable dimerisation therefore appears to require repeats 5 and 6. Based on these data a model of gelation factor architecture is presented. We suggest an arrangement of the chains where only the carboxy-terminal repeats interact as was observed for filamin/ABP280, the mammalian homologue of gelation factor.

• McCoy AJ, Fucini P, Noegel AA, Stewart M
• Structural basis for dimerization of the Dictyostelium gelation factor (ABP120) rod.
• Nat Struct Biol. 1999; 6: 836-41

Gelation factor (ABP120) is one of the principal actin-cross-linking proteins of Dictyostelium discoideum. The extended molecule has an N-terminal 250-residue actin-binding domain and a rod constructed from six 100-residue repeats that have an Ig fold. The ability to dimerize is crucial to the actin cross-linking function of gelation factor and is mediated by the rod in which the two chains are arranged in an antiparallel fashion. We report the 2.2 A resolution crystal structure of rod domains 5 and 6, which shows that dimerization is mediated primarily by rod domain 6 and is the result of a double edge-to-edge extension of beta-sheets. Thus, contrary to earlier proposals, the chains of the dimeric gelation factor molecule overlap only within domain 6, and domains 1-5 do not pair with domains from the other chain. This information allows construction of a model of the gelation factor molecule and suggests how the chains in the related molecule filamin (ABP280) may interact.

• Loo DT, Kanner SB, Aruffo A
• Filamin binds to the cytoplasmic domain of the beta1-integrin. Identification of amino acids responsible for this interaction.
• J Biol Chem. 1998; 273: 23304-12

Integrins play an important role in regulating cell adhesion, motility, and activation. In an effort to identify intracellular proteins expressed by activated T cells that interact with the cytoplasmic domain of beta1-integrin (CD29), we used the beta1-integrin cytoplasmic domain as bait in the yeast two-hybrid system. Here we report that the cytoplasmic domain of beta1-integrin specifically interacts with the cytoskeletal protein filamin. This interaction required all but the most carboxyl-terminal three residues of the cytoplasmic domain of beta1, and the carboxyl-terminal 477 residues of filamin containing the terminal 4. 5 approximately 96-residue tandem repeats of filamin. To verify this interaction in vivo, we showed that filamin specifically coprecipitated with beta1 in mammalian cells. We also showed that recombinant filamin chimeric proteins were able to bind to the beta1 cytoplasmic domain in vitro. We observed that a subset of single point mutations in the cytoplasmic domain of beta1, which had been previously reported to impair its function, disrupt the interaction between beta1 and filamin. Taken together, these findings suggest that the interaction between beta1 and filamin, which in turn can bind actin, provides a mechanism for the interaction of this cell surface receptor with cytoskeletal proteins and that this interaction plays a role in normal receptor function.

• Pfaff M, Liu S, Erle DJ, Ginsberg MH
• Integrin beta cytoplasmic domains differentially bind to cytoskeletal proteins.
• J Biol Chem. 1998; 273: 6104-9

Integrin cytoplasmic domains connect these receptors to the cytoskeleton. Furthermore, integrin-cytoskeletal interactions involve ligand binding (occupancy) to the integrin extracellular domain and clustering of the integrin. To construct mimics of the cytoplasmic face of an occupied and clustered integrin, we fused the cytoplasmic domains of integrin beta subunits to an N-terminal sequence containing four heptad repeat sequences. The heptad repeats form coiled coil dimers in which the cytoplasmic domains are parallel dimerized and held in an appropriate vertical stagger. In these mimics we found 1) that both conformation and protein binding properties are altered by insertion of Gly spacers C-terminal to the heptad repeat sequences; 2) that the cytoskeletal proteins talin and filamin are among the polypeptides that bind to the integrin beta1A tail. Filamin, but not talin binding, is enhanced by the insertion of Gly spacers; 3) binding of both cytoskeletal proteins to beta1A is direct and specific, since it occurs with purified talin and filamin and is inhibited in a point mutant (beta1A(Y788A)) or in splice variants (beta1B, beta1C) known to disrupt cytoskeletal associations of beta1 integrins; 4) that the muscle-specific splice variant, beta1D, binds talin more tightly than beta1A and is therefore predicted to form more stable cytoskeletal associations; and 5) that the beta7 cytoplasmic domain binds filamin better than beta1A. The structural specificity of these associations suggests that these mimics offer a useful approach for the analysis of the interactions and structure of the integrin cytoplasmic face.

• Takafuta T, Wu G, Murphy GF, Shapiro SS
• Human beta-filamin is a new protein that interacts with the cytoplasmic tail of glycoprotein Ibalpha.
• J Biol Chem. 1998; 273: 17531-8

We have cloned and sequenced a 9.4-kilobase cDNA specifying a new 280-kDa protein interacting with the cytoplasmic tail of glycoprotein (Gp) Ibalpha and showing considerable homology to actin-binding protein 280 (ABP-280) and chicken retinal filamin. We term this protein human beta-filamin. The gene for beta-filamin localizes to chromosome 3p14.3-p21.1. beta-Filamin mRNA expression was observed in many tissues and in cultured human umbilical vein endothelial cells (HUVECs); only minimal expression was detected in platelets and the megakaryocytic cell line CHRF-288. Like ABP-280, beta-filamin contains an NH2-terminal actin-binding domain, a backbone of 24 tandem repeats, and two "hinge" regions. A polyclonal antibody to the unique beta-filamin first hinge sequence identifies a strong 280-kDa band in HUVECs but only a weak band in platelets, and stains normal human endothelial cells in culture and in situ. We have confirmed the interaction of beta-filamin and GpIbalpha in platelet and HUVEC lysates. In addition, using two-hybrid analysis with deletion mutants, we have localized the binding domain for GpIbalpha in beta-filamin to residues 1862-2148, an area homologous to the GpIbalpha binding domain in ABP-280. beta-Filamin is a new member of the filamin family that may have significance for GpIbalpha function in endothelial cells and platelets.

• XuW f, Xie Z, Chung DW, Davie EW
• A novel human actin-binding protein homologue that binds to platelet glycoprotein Ibalpha.
• Blood. 1998; 92: 1268-76

Glycoprotein (GP)Ib-IX-V is one of the major transmembrane complexes present on the platelet surface. Its extracellular domain binds von Willebrand factor (vWF) and thrombin, while its intracellular domain associates tightly with the cytoskeleton through the actin-binding protein (ABP)-280, also known as filamin. In the present study, a full-length cDNA coding for a human ABP homologue has been cloned and sequenced. This protein was identified by the yeast two-hybrid screening procedure via its interaction with the intracellular domain of GPIbalpha. Initially, a 1.3-kb partial cDNA was isolated from a megakaryocyte-like cell line (K562) cDNA library followed by a full-length cDNA of 9.4 kb that was identified in a human placenta library. The full-length cDNA encoded a protein of 2,578 amino acids with a calculated molecular weight of 276 kD (ABP-276). The amino terminal 248 amino acids contained an apparent actin binding domain followed by 24 tandem repeats each containing about 96 amino acids. The amino acid sequence of the protein shared a high degree of homology with human endothelial ABP-280 (70% identity) and chicken filamin (83% identity). However, the 32 amino acid Hinge I region in ABP-280 that contains a calpain cleavage site conferring flexibility on the molecule, was absent in the homologue. An isoform containing a 24 amino acid insertion with a unique sequence at the missing Hinge I region was also identified (ABP-278). This isoform resulted from alternative RNA splicing. ABP-276 and/or ABP-278 were present in all tissues examined, but the relative amount varied in that some tissue contained both forms, while other tissue contained predominately one or the other.

• Gorlin JB et al.
• Human endothelial actin-binding protein (ABP-280, nonmuscle filamin): a molecular leaf spring.
• J Cell Biol. 1990; 111: 1089-105

Actin-binding protein (ABP-280, nonmuscle filamin) is a ubiquitous dimeric actin cross-linking phosphoprotein of peripheral cytoplasm, where it promotes orthogonal branching of actin filaments and links actin filaments to membrane glycoproteins. The complete nucleotide sequence of human endothelial cell ABP cDNA predicts a polypeptide subunit chain of 2,647 amino acids, corresponding to 280 kD, also the mass derived from physical measurements of the native protein. The actin-binding domain is near the amino-terminus of the subunit where the amino acid sequence is similar to other actin filament binding proteins, including alpha-actinin, beta-spectrin, dystrophin, and Dictyostelium abp-120. The remaining 90% of the sequence comprises 24 repeats, each approximately 96 residues long, predicted to have stretches of beta-sheet secondary structure interspersed with turns. The first 15 repeats may have substantial intrachain hydrophobic interactions and overlap in a staggered fashion to yield a backbone with mechanical resilience. Sequence insertions immediately before repeats 16 and 24 predict two hinges in the molecule near points where rotary-shadowed molecules appear to swivel in electron micrographs. Both putative hinge regions are susceptible to cleavage by proteases and the second also contains the site that binds the platelet glycoprotein Ib/IX complex. Phosphorylation consensus sequences are also located in the hinges or near them. Degeneracy within every even-numbered repeat between 16 and 24 and the insertion before repeat 24 may convert interactions within chains to interactions between chains to account for dimer formation within a domain of 7 kD at the carboxy-terminus. The structure of ABP dimers resembles a leaf spring. Interchain interactions hold the leaves firmly together at one end, whereas intrachain hydrophobic bonds reinforce the arms of the spring where the leaves diverge, making it sufficiently stiff to promote high-angle branching of actin filaments. The large size of the leaves, their interruption by two hinges and flexible actin-binding site, facilitate cross-linking of widely dispersed actin filaments.

• Hock RS, Davis G, Speicher DW
• Purification of human smooth muscle filamin and characterization of structural domains and functional sites.
• Biochemistry. 1990; 29: 9441-51

A method was developed to purify human smooth muscle filamin in high yield and structural domains were defined by using mild proteolysis to dissect the molecule into intermediate-sized peptides. Unique domains were defined and aligned by using high-resolution peptide mapping of iodinated peptides on cellulose plates. The amino- and carboxyl-terminal orientation of these domains within the molecule was determined by amino acid sequence analysis of several aligned peptides. In addition to the three unique domains which were identified, a number of smaller and larger fragments were also characterized and aligned within the intact molecule. These structural domains and related peptides provide a useful set of defined fragments for further elucidation of structure-function relationships. The two known functionally important binding sites of filamin, the self-association site and the actin-binding site, have been localized. Self-association of two monomers in a tail-to-tail orientation involves a small protease-sensitive region near the carboxyl terminal of the intact polypeptide chain. Sedimentation assays indicate that an actin-binding site is located near the blocked amino terminal of the filamin molecule. Sequences derived from large peptides mapping near the amino terminal show homology to the amino-terminal actin-binding site of alpha-actinin (chicken fibroblast and Dictyostelium), Dictyostelium 120-kDa actin gelation factor, beta-spectrin (human red cell and Drosophila), and human dystrophin. This homology is particularly interesting for two reasons. The functional form of filamin is single stranded, in contrast to alpha-actinin and spectrin which are antiparallel double-stranded actin cross-linkers. Also, no homology to the spectrin-like segments which comprise most of the mass of spectrin, alpha-actinin, and dystrophin was found. Instead, the sequence of a domain located near the center of the filamin molecule (tryptic 100-kDa peptide, T100) shows homology to the published internal repeats of the Dictyostelium 120-kDa actin gelation factor. On the basis of these results, a model of human smooth muscle filamin substructure is presented. Also, comparisons of human smooth muscle filamin, avian smooth muscle filamin, and human platelet filamin are reported.

Metabolism (metabolic pathways involving proteins which contain this domain)

% proteins involved	KEGG pathway ID	Description
50.00	map04510	Focal adhesion
50.00	map04010	MAPK signaling pathway

This information is based on mapping of SMART genomic protein database to KEGG orthologous groups. Percentage points are related to the number of proteins with IG_FLMN domain which could be assigned to a KEGG orthologous group, and not all proteins containing IG_FLMN domain. Please note that proteins can be included in multiple pathways, ie. the numbers above will not always add up to 100%.

Structure (3D structures containing this domain)

3D Structures of IG_FLMN domains in PDB

PDB code	Title
1ksr	THE REPEATING SEGMENTS OF THE F-ACTIN CROSS-LINKING GELATION FACTOR (ABP-120) HAVE AN IMMUNOGLOBULIN FOLD, NMR, 20 STRUCTURES
1qfh	DIMERIZATION OF GELATION FACTOR FROM DICTYOSTELIUM DISCOIDEUM: CRYSTAL STRUCTURE OF ROD DOMAINS 5 AND 6
1v05	Dimerization of human Filamin C: crystal structure of the domain 24
1wlh	Molecular structure of the rod domain of Dictyostelium filamin
2aav	Solution NMR structure of Filamin A domain 17
2bp3	Crystal structure of Filamin A domain 17 and GPIb alpha cytoplasmic domain complex
2brq	Crystal structure of the filamin A repeat 21 complexed with the integrin beta7 cytoplasmic tail peptide
2d7m	Solution structure of the 14th Filamin domain from human Filamin C
2d7n	Solution structure of the 16th Filamin domain from human Filamin C
2d7o	Solution structure of the 17th Filamin domain from human Filamin C
2d7p	Solution structure of the 22th Filamin domain from human Filamin C
2d7q	Solution structure of the 23th Filamin domain from human Filamin C
2di7	Solution structure of the filamin domain from human BK158_1 protein
2di8	Solution structure of the 19th filamin domain from human Filamin-B
2di9	Solution structure of the 9th filamin domain from human Filamin-B
2dia	Solution structure of the 10th filamin domain from human Filamin-B
2dib	Solution structure of the 11th filamin domain from human Filamin-B
2dic	Solution structure of the 12th filamin domain from human Filamin-B
2dj4	Solution structure of the 13th filamin domain from human Filamin-B
2dlg	Solution structure of the 20th Filamin domain from human Filamin-B
2dmb	Solution structure of the 15th Filamin domain from human Filamin-B
2dmc	Solution structure of the 18th Filamin domain from human Filamin-B
2ds4	Solution structure of the filamin domain from human tripartite motif protein 45
2e9i	Solution structure of the N-terminal extended 20th Filamin domain from human Filamin-B
2e9j	Solution structure of the 14th filamin domain from human Filamin-B
2ee6	Solution structure of the 21th filamin domain from human Filamin-B
2ee9	Solution structure of the 16th filamin domain from human Filamin-B
2eea	Solution structure of the 17th filamin domain from human Filamin-B
2eeb	Solution structure of the 22th filamin domain from human Filamin-B
2eec	Solution structure of the 23th filamin domain from human Filamin-B
2eed	Solution structure of the 24th filamin domain from human Filamin-B
2j3s	Crystal structure of the human filamin A Ig domains 19 to 21
2jf1	CRYSTAL STRUCTURE OF THE FILAMIN A REPEAT 21 COMPLEXED WITH THE INTEGRIN BETA2 CYTOPLASMIC TAIL PEPTIDE
2k3t	Solution Structure of IG-Like Domain 23 from Human Filamin A
2k7p	Filamin A Ig-like domains 16-17
2k7q	Filamin A Ig-like domains 18-19
2k9u	Solution NMR structure of the Filamin-migfilin complex
2mtp	2MTP
2n62	2N62
2nqc	Crystal structure of ig-like domain 23 from human filamin C
2w0p	Crystal structure of the filamin A repeat 21 complexed with the migfilin peptide
3cnk	Crystal Structure of the dimerization domain of human filamin A
3isw	Crystal structure of filamin-A immunoglobulin-like repeat 21 bound to an N-terminal peptide of CFTR
3rgh	Structure of filamin A immunoglobulin-like repeat 10 from Homo sapiens
3v8o	Human Filamin C Ig - like Domains 4 and 5
4b7l	Crystal Structure of Human Filamin B Actin Binding Domain with 1st Filamin Repeat
4m9p	Crystal structure of the human filamin A Ig-like domains 3-5
4mgx	Crystal structure of human filamin C domains 4-5 and GPIB alpha cytoplasmic domain complex
4p3w	4P3W
4umg	4UMG
5dcp	5DCP

Links (links to other resources describing this domain)

• INTERPRO: IPR001298