Crystal Structure Analysis of Sarcoplasmic-Calcium-Binding Protein: An Allergen in Scylla paramamosain

Abstract

The structure of allergenic proteins provides important information about the binding of allergens to antibodies. In this study, the crystal structure of Scy p 4 with a resolution of 1.60 Å was obtained by X-ray diffraction. Epitope mapping of Scy p 4 revealed that linear epitopes are located on the surface of Scy p 4. Also, conformational epitopes are mostly located in the structural conservative region. Further structural comparison, surface electrostatic potential, and hydrogen bond force analysis showed that mutation of Asp 70 and Asp 18/20/70 would lead to calcium-binding capacity being lost and destruction of allergenicity. Furthermore, a comparative analysis of structure showed that sarcoplasmic-calcium-binding protein (SCP) had high sequence, secondary, and spatial structural identity in crustaceans, which may be an important factor leading to cross-reactivity among crustaceans. The structure of Scy p 4 provides a template for epitope evaluation and localization of SCPs, which will help to reveal cross-reactivity among species.

Mutation of Disulfide Bond Sites Reduces the Immunoreactivity of Cra a 4 by Changing the Structural Characteristics

“…SCP was identified as a heat-resistance allergen. In addition, SCP belongs to the EF-hand superfamily, so the change of structure could affect the allergenicity . In a previous study, the disulfide bond, two conformational mimotopes, or Ca 2+ -binding regions of Cra a 4 were identified. , However, the structure–allergenicity relationship of Cra 4 was not assessed.…”

Purification, Expression, and Characterization of Sarcoplasmic Calcium Binding Protein: A Novel Allergen of Portunus trituberculatus

“…Key amino acids are amino acids belonging to several epitopes or bioactive sites, which are essential for the structures, physicochemical properties, and bioactivity of allergens. Chen et al mutated the key amino acids in conformational epitopes and calcium-binding sites of SCP, that resulted in reduced α-helical content, decreased capacity to bind calcium, mitigated allergenicity, and the decline of thermal and pH stability. , Therefore, the stability distinctions were speculatively caused by the differences in their key amino acids and structures, that need to be further explored and may contribute to the reduction in allergenicity.…”

“…26 The results of CD spectra and PSIPRED displayed around 60% α-helix in SCP, which is consistent with the 61% helix in Scy p 4 and 60.62% α-helix in Lit v 4, as previously reported. 11,27 In previous studies, the IgE-binding activity of Scy p 4 significantly decreased after the mutations of calcium binding sites or the glycosylation with glucose. 28,29 Since calcium binding sites and glycosylation are perhaps associated with the IgE-binding capacity, the calcium binding sites and glycosylation sites were analyzed in this study for feasible following research on reducing the allergenic potency of SCP.…”

Mechanism of Targeted Regulation of Ovalbumin Epitopes by Pulsed Electric Field-Assisted Alcalase Treatment

“…Phylogenetic tree analysis was constructed by MEGA11's neighbor-joining tree. 25 Nano-HPLC MS/MS Analysis. Based on the method of Li et al, 18 the influence of PEF-assisted Alcalase treatment on the linear epitopes of allergen OVA was determined, and the mechanism of the regulation of potential allergenicity by PEF-assisted Alcalase treatment was revealed.…”

“…Amino acid sequence alignment of OVA from different species was performed by MEGA11 software. Phylogenetic tree analysis was constructed by MEGA11’s neighbor-joining tree …”