Fel d 1

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Major allergen I polypeptide chain 2
Fel d 1.png
Crystallographic structure of the Fel d 1 dimer, the primary allergen present in cat saliva.[1]
Symbol CH2
Alt. symbols Fel d I, AG4, Allergen Cat-1
Entrez 677879
UniProt P30440
Allergen Fel d I-B chain
PDB 2ejn EBI.jpg
structural characterization of the tetrameric form of the major cat allergen fel d 1
Symbol Feld-I_B
Pfam PF09252
Pfam clan CL0370
InterPro IPR015332
SCOP 1puo

Fel d 1 is a protein that in cats is encoded by the CH1 (chain 1/Fel d 1-A) and CH2 (chain 2/Fel d 1-B) genes.[2][3]

Fel d 1, produced largely in cat saliva and sebaceous glands, is the primary allergen present on cats and kittens.[1] Fel d 1 is also produced by cat skin itself.[4] The protein is of an unknown function to the animal but causes an IgG or IgE reaction in sensitive humans (either as an allergic or asthmatic response). Removal of soft surfaces in the home (carpet, furniture), frequent washings of bed linens, HEPA filters and even washing cats has been proven to reduce the amounts of Fel d 1 present in the home.

Female cats produce a lower level of Fel d 1 than males, and neutered males produce a lower level of Fel d 1 than unneutered males.[5]

Neutered males produce Fel d 1 in levels similar to females (both intact and spayed females produce Fel d 1 in similar levels). Even though females and neutered males produce Fel d 1 in lower levels, they still produce enough to cause allergic symptoms in sensitive individuals.

A variant of Fel-D1 is present in the venom of the slow loris (Primate: Nycticebus). Slow lorises are one of only a few venomous mammals and the only known venomous primate, possessing a dual-composite venom of saliva and brachial gland exudate (BGE) [6]. The BGE possesses a protein resembling Fel-D1, which may effect host species as an allergen as a constitute of the venom, and possess a communicative function.


The complete quaternary structure of Fel d 1 has been determined.[1] The allergen is a tetrameric glycoprotein consisting of two disulfide-linked heterodimers of chains 1 and 2. Fel d 1 chains 1 and 2 share structural similarity with uteroglobin, a secretoglobin superfamily member; chain 2 is a glycoprotein with N-linked oligosaccharides. Both chains share an all alpha-helical structure.[1]

See also[edit]


  1. ^ a b c d PDB: 1PUO​; Kaiser L, Grönlund H, Sandalova T, Ljunggren HG, van Hage-Hamsten M, Achour A, Schneider G (September 2003). "The crystal structure of the major cat allergen Fel d 1, a member of the secretoglobin family". J. Biol. Chem. 278 (39): 37730–5. doi:10.1074/jbc.M304740200. PMID 12851385. 
  2. ^ Morgenstern JP, Griffith IJ, Brauer AW, Rogers BL, Bond JF, Chapman MD, Kuo MC (November 1991). "Amino acid sequence of Fel dI, the major allergen of the domestic cat: protein sequence analysis and cDNA cloning". Proc. Natl. Acad. Sci. U.S.A. 88 (21): 9690–4. doi:10.1073/pnas.88.21.9690. PMC 52784Freely accessible. PMID 1946388. 
  3. ^ Griffith IJ, Craig S, Pollock J, Yu XB, Morgenstern JP, Rogers BL (April 1992). "Expression and genomic structure of the genes encoding FdI, the major allergen from the domestic cat". Gene. 113 (2): 263–8. doi:10.1016/0378-1119(92)90405-E. PMID 1572548. 
  4. ^ DABROWSKI, A; VANDERBREMPT, X; SOLER, M; SEGURET, N; LUCCIANI, P; CHARPIN, D; VERVLOET, D. "Cat skin as an important source of Fel d I allergen". Journal of Allergy and Clinical Immunology. 86 (4): 462–465. doi:10.1016/S0091-6749(05)80200-3. 
  5. ^ Sex difference in Fel d 1 allergen production. http://www.jacionline.org/article/S0091-6749(96)70238-5/fulltext . Accessed 31 Oct 2016.
  6. ^ Nekaris, K. Anne-Isola; Moore, Richard S.; Rode, E. Johanna; Fry, Bryan G. (2013-09-27). "Mad, bad and dangerous to know: the biochemistry, ecology and evolution of slow loris venom". Journal of Venomous Animals and Toxins including Tropical Diseases. 19: 21. doi:10.1186/1678-9199-19-21. ISSN 1678-9199. 

This article incorporates text from the public domain Pfam and InterPro IPR015332