Purification, Physicochemical Properties, and Epitope Analysis of Sarcoplasmic Calcium-Binding Protein from Penaeus vannamei

Sarcoplasmic-calcium-binding protein (SCP) was isolated, purified and identified from Penaeus vannamei. Meanwhile, its physicochemical properties (immunoactivity, thermal stability, pH stability and digestive stability), secondary structures and epitopes were studied. The results showed that the purified protein, which was obtained by successive steps of crude protein extraction, ammonium sulfate fractionation and anion exchange chromatography and exhibited a molecular mass of 21.6 kDa, was identified as SCP with a peptide coverage of 93.26%. SCP had strong immunoactivity, which decreased during heat treatment (≥ 65 ℃) and under strongly acidic and alkaline conditions. SCP had strong stability against intestinal fluid digestion, but poor stability against gastric fluid digestion. The secondary structure of SCP consisted of 26% α-helix, 16.9% β-sheet, 17.5% β-turn, and 39.6% random coil. Eight epitopes in SCP were predicted and identified using bioinformatics tools combined with immunological techniques.