Chang L S, Lin S R, Chang C C
Department of Biochemistry, Kaohsiung Medical College, Kaohsiung, Taiwan, ROC.
Biochem Mol Biol Int. 1995 Sep;37(1):117-23.
In contrast to observations made with S. aureus V8 protease-digest hydrolysates, the antigenic structures of reduced and S-carboxymethylated (RCM)-cobrotixin were notably affected following hydrolysis of RCM-cobrotoxin with chymotrypsin. The peptide separated from the V8 protease-digest hydrolysates with a sequence at positions 22-38 of cobrotoxin exhibited a nearly equal reactivity toward the anti-RCM-cobrotoxin antibodies as RCM-cobrotoxin. Chymotryptic cleavage on this segment caused a precipitous drop in the antigenicity of RCM-cobrotoxin. Alternatively, the N-terminal and C-terminal regions of RCM-cobrotoxin encompassed other antigenic determinants which exhibited low reactivities toward anti-RCM-cobrotoxin antibodies. The epitope structures of RCM-cobrotoxin are in line with those predicted from the hydrophobicity profile of cobrotoxin, but the notably immunoreactive region in the C-terminal region of native toxin molecule (Ref. 1) cannot be predicted from analysis of its primary structure. Moreover, RCM-cobrotoxin had a superior reactivity toward anti-RCM-cobrotoxin antibodies than cobrotoxin did. These results indicate that the epitope structures in RCM-cobrotoxin and cobrotoxin are different.
与用金黄色葡萄球菌V8蛋白酶消化水解产物的观察结果相反，用胰凝乳蛋白酶水解RCM-眼镜蛇毒素后，还原和S-羧甲基化（RCM）-眼镜蛇毒素的抗原结构受到显著影响。从V8蛋白酶消化水解产物中分离出的肽，其在眼镜蛇毒素22-38位的序列对抗RCM-眼镜蛇毒素抗体的反应性与RCM-眼镜蛇毒素几乎相同。该片段上的胰凝乳蛋白酶切割导致RCM-眼镜蛇毒素的抗原性急剧下降。另外，RCM-眼镜蛇毒素的N端和C端区域包含其他抗原决定簇，这些决定簇对抗RCM-眼镜蛇毒素抗体的反应性较低。RCM-眼镜蛇毒素的表位结构与从眼镜蛇毒素的疏水性图谱预测的结构一致，但天然毒素分子C端区域中显著的免疫反应区域（参考文献1）无法从其一级结构分析中预测。此外，RCM-眼镜蛇毒素对抗RCM-眼镜蛇毒素抗体的反应性比眼镜蛇毒素更高。这些结果表明RCM-眼镜蛇毒素和眼镜蛇毒素中的表位结构不同。
