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 Asp70 and Asp18/20/70 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.