A Crystal Structure\nof Pro c 2 Provides Insights into\nCross-Reactivity of Aquatic Allergens from the Phosphagen Kinase Family

Arginine kinase (AK) from the phosphagen kinase family\nis a cross-reactive\nshellfish allergen. Structurally related cross-reactive allergens\nare involved in the pathogenesis of allergic symptoms. This study\naimed to unravel the cross-reactivity of AK from a structural perspective.\nThe crystal structure of Procambarus clarkii AK (Pro c 2) was resolved at 1.57 Å resolution, which showed\na well-conserved structure not only to shellfish AKs but also to fish\ncreatine kinase (CK), another allergen from the phosphagen kinase\nfamily. In Western blot, the CK corresponding protein in fish muscles\nwas found to be reactive with AK-specific immunoglobulin (Ig) G. Recombinant\nPro c 2 (rPro c 2) and CKs from Lateolabrax japonicus (rCK-<i>L</i>) and Ctenopharyngodon idell (rCK-<i>C</i>) were then produced, and the IgE reactivity\nof rCK-<i>L</i> and rCK-<i>C</i>, as well as their\nIgG/IgE cross-reactivity with rPro c 2, was confirmed by immunological\nassays. This study demonstrated the cross-reactivity among aquatic\nallergens from the phosphagen kinase family due to their structural\nsimilarity.