Abstract
Background: Lipocalins play a role in the cellular trafficking of pheromones and are involved in allergic responses to domestic pets. However, the cross-reactivity among allergens of this group has been poorly explored, and the pheromone linking capacity is not well characterized. The aim of this study was to explore cross-reactive epitopes and pheromone linking capacity among Rat n 1 and homologues in domestic pets through an in silico approach. Methods: ElliPro and BepiPred in silico tools were used to predict B cell linear and cross-reactive epitopes. The pheromone linking capacity was explored by docking virtual screening with 2-ethylhexanol, 2,5-dimethylpyrazine, 2-sec-butyl-4,5-dihydrothiazole, and 2-heptanone ligands. Results: According to the analysis, Rat n 1 shares 52% identity with Equ c 1, Can f 6, Fel d 4, and Mus m 1 allergens. The overlapping structures assay revealed high structural homology (root mean square deviation < 1). Four lineal and three discontinuous epitopes were predicted on Ra t n 1. A lineal epitope located between amino acids residues 24 and 36 was highly conserved on all allergens explored. A cross-reactive discontinuous epitope (T142, K143, D144, L145, S146, S147, D148, K152, L170, T171, T173, D174) was also found. Docking molecular simulations revealed the active site, and we identified the properties of the binding of four pheromones and the binding potential of Rat n 1. Critical residues for interactions are reported in this study. Conclusions: We identified some possible allergens from Rattus norvegicus, and those allergens could have cross-reactivity with allergens from some animals. The results need to be confirmed with in vitro studies and could be utilized to contribute to immunotherapy and reduce allergic diseases related to lipocalins.
Highlights
Lipocalins are among the most important indoor/outdoor groups of animal allergens
A comparison of the secondary structural elements of Rattus norvegicus (Rat) n 1 with the structures listed in Table 1 revealed backbone atomic RMSD values between 0.3 and 0.95 Ă , with Mus m 1 showing the most closely related structure and sequence homology to Rat n 1
The closest structural homology was found on the α-helical amino acid sequence spanning region on Rat n 1 containing nine conserved residues (IKEKFAK-L) (Figure 2)
Summary
Lipocalins are among the most important indoor/outdoor groups of animal allergens. For some, the protein structure has been resolved, but their functions are still elusive. Its structure is like a conventional lipocalin with eight antiparallel ÎČ chains forming a single beta sheet and an α helix to create a pocket for ligand binding, very similar to that of other allergens, such as Mus m 1, the mouseâs main allergen, with a highly conserved identity. The cross-reactivity among allergens of this group has been poorly explored, and the pheromone linking capacity is not well characterized. The aim of this study was to explore cross-reactive epitopes and pheromone linking capacity among Rat n 1 and homologues in domestic pets through an in silico approach. Methods: ElliPro and BepiPred in silico tools were used to predict B cell linear and cross-reactive epitopes. A lineal epitope located between amino acids residues 24 and 36 was highly conserved on all allergens explored. The results need to be confirmed with in vitro studies and could be utilized to contribute to immunotherapy and reduce allergic diseases related to lipocalins
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