The Toxicological Intersection between Allergen and Toxin: A Structural Comparison of the Cat Dander Allergenic Protein Fel d1 and the Slow Loris Brachial Gland Secretion Protein

Abstract

Slow lorises are enigmatic animal that represent the only venomous primate lineage. Their defensive secretions have received little attention. In this study we determined the full length sequence of the protein secreted by their unique brachial glands. The full length sequences displayed homology to the main allergenic protein present in cat dander. We thus compared the molecular features of the slow loris brachial gland protein and the cat dander allergen protein, showing remarkable similarities between them. Thus we postulate that allergenic proteins play a role in the slow loris defensive arsenal. These results shed light on these neglected, novel animals.

Hello, kitty: could cat allergy be a form of intoxication?

“…Sequence IDs, species and common names are presented in Additional file 1 (species for which there are insufficient or unavailable data are shown in Additional file 2 ). Here, besides the full sequence of N. javanicus BGE protein recently obtained by Scheib et al [ 13 ], two additional sequences, for N. coucang and N. pygmaeus , were found by database mining. The sequence alignments ( Figure 1 ) reveal the high conservation of felid Fel d 1 and their more distant similarity to sequences for slow loris ( Nycticebus spp., NCBI: txid9469).…”

“…The sequence alignments ( Figure 1 ) reveal the high conservation of felid Fel d 1 and their more distant similarity to sequences for slow loris ( Nycticebus spp., NCBI: txid9469). The glycosylation site is conserved for all species, with a proposed shift from N- to O-glycosylation in N. javanicus [ 13 ] being also found for N. coucang . One of the disulfide bonds (Cys pair 3) is not conserved in these alignments, due to shorter chain 1 sequences for most of the inspected species.…”

“…Despite its recurrence, the shortening of sequences at their C-terminus due to genetic sequencing issues cannot be discarded. Calcium ion binding sites [ 17 , 21 ] are more conserved than the interface hydrophobic cluster [ 13 , 17 ]. The Fel d 1 dimer-of-dimers interface is less conserved than the core cavity-bearing dimers, as shown in Figure 2 .…”

“…It has been found in dwellings, classrooms, cinemas, hotels, cars, buses, and clothing [68][69][70][71][72][73]. It has even been detected in the isolated Tristan da Cunha Island twenty years after all cats were removed from its territory [74], and in the Greenland inland ice shelf, were cats are unlikely to have lived [13]. Fel d 1 is found in particle sizes as small as 4.7 µm, making it suitable for airborne transportation [75,76].…”

“…When bitten by the animal in such “loaded” state, humans (and other animals, including loris conspecifics) have varied physiological responses, from nothing to tissue decay, anaphylactic shock, and death [ 3 , 4 ]. The BGE protein has been recently shown to closely resemble Fel d 1, the major cat allergen [ 12 , 13 ]. This connection between venom and allergen led to an inspection of Fel d 1 in a broader, physiological context, since no pinpointed function has been ascribed to this protein [ 14 ].…”