SB-P02-189 IN SILICO STRUCTURAL STUDIES AS A COMPLEMENT TO EPITOPIC MAPPING OF THE ALLERGENIC SOY PROTEIN Gly m Bd 30K (P34)

ANGELA MARÍA CANDREVA; DOCENA GUILLERMO H.; ANA CAUERHFF

Buenos Aires

Congreso; SAIB 2020- BIOCELL LVI SAIB Meeting ?XV SAMIGE Meeting; 2020

Sociedad Argentina de Investigación Bioquímica y Biología Molecular

SB-P02-189 IN SILICO STRUCTURAL STUDIES AS A COMPLEMENT TO EPITOPIC MAPPING OF THE ALLERGENIC SOY PROTEIN Gly m Bd 30K (P34) Cauerhff A1 , Candreva AM2 and Docena G2 1Depto Quim. Biol., FCEN, CONICET-UBA, 2 Inst. Est. Inmunol. Fisiopatol. (IIFP), CONICET-UNLP. E-mail: anacauer@qb.fcen.uba.ar Food allergy is caused mainly by soy, milk and eggs and comprises immune reactions generally related to IgE due to the exposure of macromolecules, mostly proteins, known as allergens. Caseins from bovine milk and different soy proteins produce allergic cross-reactions. The development of hypoallergenic soybean products or peptide-based therapies requires a detailed structural study of allergens. Several studies found that Gly m Bd 30K or P34 is one of the main soybean allergenic proteins that contain cross-reactive B and T epitopes. Those epitopes were mapped using an array of consecutive overlapping peptides spanning the allergen sequence in SPOTs assay. The molecular distribution of these B epitopes (recognized by different antibodies and patients sera) in P34 was investigated by in silico analysis. It involved 3D-structure prediction by means of homology modeling from the P34 protein sequence. The two first models of P34 were generated with Swiss Protein Workspace and the Modeller 9v7 program using the structure of procaricain and the precursor of a thermostable variant of papain from Carica papaya and papain fold-protein from seeds of Pachyrhizus erosus as templates. Additionaly, the I-Tasser Suite and the Phyre2 server was employed to model the whole P34 protein and its Nt and Ct fragments. All models were refined with the 3Drefine server and the Modrefiner algorithm, and then with the Yasara Energy Minimization server. The quality of models was evaluated with the QMEAN and WHAT IF server and their representation was made with Phymol 0.99rc6 program. The assignment of secondary structure from 3D-coordinates was performed by the 2struc Secondary Structure server, whereas its prediction from P34 primary sequence by means JPred 4 server, Jsspred, LOMETS, I-Tasser suite and the Phyre2 web portal. The best models were selected considering the prediction and the calculation from the secondary structure analysis, as well as their structural quality. Finally, three models were assessed: two models obtained from Phyre2 (entire P34 and its Nt fragment) and one from the I-Tasser server (whole P34 molecule). All models showed a high similarity with an rmsd value in the range of 1.08-1.13Å for C atoms, the main structural difference was observed in the Nt domain. The models obtained with Phyre2 server showed higher content of -helix than those from I-Tasser server; this fact is in concordance with the prediction from JPred, Pssp and LOMETS servers. The Nt domain, which contains most of the immunodominant IgG and IgE epitopes, was predominantly composed of α-helix and the Ct domain of a summation of αhelix, β-sheet and random coil structures. The complete in silico analysis demonstrated that the position of the B epitopes in P34 comprised many internal with some superficial and charge regions. These results show the possible structural reason for the conservation and the strengthening of the allergenicity of P34 after its denaturation.