For examination of the structure-activity relationship of STh, five shorter analogs of STh lacking one to five N-terminal amino acid residues of STh were synthesized. The synthetic peptides were confirmed to have the same intramolecular disulfide linkages as those in native STh. These peptides caused fluid accumulation in the intestine of suckling mice at almost the same molar levels as that of native STh. The toxicities of these peptides were also neutralized by antisera raised against native STh. These results indicated that the toxic and antigenic sites of STh are both located in the amino acid sequence between the Cys residue at the 5th position from the N-terminus and the C-terminal Tyr residue.
为了检查STh的结构-活性关系,合成了缺少1至5个STh N端
氨基酸残基的5个较短的STh类似物。合成肽被证实具有与天然 STh 相同的分子内二
硫键。这些肽在乳鼠肠道中引起液体积聚,其摩尔
水平几乎与天然 STh 相同。这些肽的毒性也被针对天然 STh 的抗血清中和。这些结果表明,STh的毒性和抗原位点均位于N端第5位Cys残基和C端Tyr残基之间的
氨基酸序列中。