EMI domain
{{Infobox protein family
| Symbol = EMI
| Name = EMI domain
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| Pfam = PF07546
| Pfam_clan =
| InterPro = IPR011489
| SMART =
| PROSITE =
| MEROPS =
| SCOP =
| TCDB =
| OPM family =
| OPM protein =
| CAZy =
| CDD =
}}
In molecular biology, the EMI domain, first named after its presence in proteins of the EMILIN family, is a small cysteine-rich protein domain of around 75 amino acids. The EMI domain is most often found at the N terminus of metazoan extracellular proteins that are forming or are compatible with multimer formation.{{cite journal |vauthors=Doliana R, Bot S, Bonaldo P, Colombatti A | title = EMI, a novel cysteine-rich domain of EMILINs and other extracellular proteins, interacts with the gC1q domains and participates in multimerization | journal = FEBS Lett. | volume = 484 | issue = 2 | pages = 164–8 |date=November 2000 | pmid = 11068053 | doi = 10.1016/S0014-5793(00)02140-2| s2cid = 38531447 | doi-access = free }} It is found in association with other domains, such as C1q, laminin-type EGF-like, collagen-like, FN3, WAP, ZP or FAS1.{{cite journal |vauthors=Callebaut I, Mignotte V, Souchet M, Mornon JP | title = EMI domains are widespread and reveal the probable orthologs of the Caenorhabditis elegans CED-1 protein | journal = Biochem. Biophys. Res. Commun. | volume = 300 | issue = 3 | pages = 619–23 |date=January 2003 | pmid = 12507493 | doi = 10.1016/S0006-291X(02)02904-2}} It has been suggested that the EMI domain could be a protein-protein interaction module, as the EMI domain of EMILIN-1 was found to interact with the C1q domain of EMILIN-2.
The EMI domain possesses six highly conserved cysteine residues, which likely form disulphide bonds. Other key features of the EMI domain are the C-C-x-G-[WYFH] pattern, a hydrophobic position just preceding the first cysteine (Cys1) of the domain and a cluster of hydrophobic residues between Cys3 and Cys4. The EMI domain could be made of two sub-domains, the fold of the second one sharing similarities with the C-terminal sub-module characteristic of EGF-like domains.
Proteins known to contain an EMI domain include:
- Vertebrate Emilins, extracellular matrix glycoproteins.
- Vertebrate Multimerins, extracellular matrix glycoproteins.
- Vertebrate Emu proteins, which could interact with several different extracellular matrix components and serve to connect and integrate the function of multiple partner molecules.
- Vertebrate beta-IG-H3.
- Vertebrate osteoblast-specific factor 2 (OSF-2).
- Mammalian NEU1/NG3 proteins.
- Drosophila midline fasciclin.
- Caenorhabditis elegans ced-1, a transmembrane receptor that mediates cell corpse engulfment.