Immunochemical studies of human fibrinopeptide A using synthetic peptide homologues.
Immunochemical studies of human fibrinopeptide A using synthetic peptide homologues.
复制标题
使用合成肽同系物对人纤维蛋白肽 A 进行免疫化学研究。
作者：
G. Wilner;H. Nossel;R. Canfield;V. Butler
先前的研究表明，兔抗血清R2和R33对人纤维蛋白肽A的交叉反应性与纤维蛋白原和含纤维蛋白肽A的纤维蛋白原分子片段有显著差异。抗血清特异性是通过比较合成片段和酶切纤维蛋白肽A分子与完整纤维蛋白肽序列（α 1-16）结合对放射性标记酪氨酸纤维蛋白肽A的抑制作用来表征的。通过十二肽（α α 5-16）合成的cooh末端同源物与R33抗血清的免疫反应性低于16%，与纤维蛋白原和含有纤维蛋白肽a的纤维蛋白原片段广泛交叉反应。相比之下，合成的cooh末端十肽（α 7-16）与R2抗血清具有100%的免疫反应性，与纤维蛋白原和含有纤维蛋白肽a的纤维蛋白原片段的交叉反应最小。小于α - 7-16的合成同源物，如α - 9-16和α - 7-11，与R2抗血清的反应很小。羧肽酶B对纤维蛋白肽A的消化保留了小于其初始R2抗血清免疫反应性的25%。由此可见，R2免疫反应性的抗原决定因素完全位于纤维蛋白肽A的cooh末端十位残基序列内，而ph -8、Asp-7和Arg-16对R2免疫反应性有显著影响。当纤维蛋白肽附着在其亲本α链上时，R2抗原决定因子似乎比R33决定因子更难以与抗体发生反应（Canfield et al., 1976）。讨论了一种可能的封存机制。
Previous studies have indicated that rabbit antisera R2 and R33 to human fibrinopeptide A differ markedly in terms of cross-reactivity with fibrinogen and fibrinopeptide A-containing fragments of the fibrinogen molecule. Antiserum specificity was characterized by comparison of inhibition of binding to radiolabeled tyrosyl fibrinopeptide A produced by synthetic fragments and enzymatic digests of the fibrinopeptide A molecule vs. the complete fibrinopeptide sequence (Aalpha 1-16). Synthetic COOH-terminal homologues through the dodecapeptide (Aalpha 5-16) exhibited less than 16% immunoreactivity with R33 antiserum, which cross-reacts extensively with fibrinogen and fibrinopeptide A-containing fibrinogen fragments. In contrast, the synthetic COOH-terminal decapeptide (Aalpha 7-16) gave 100% immunoreactivity with R2 antiserum, which cross-reacts minimally with fibrinogen and fibrinopeptide A-containing fibrinogen fragments. Synthetic homologues smaller than Aalpha 7-16, such as Aalpha9-16 and Aalpha 7-11, reacted only minimally with R2 antiserum. Carboxypeptidase B digests of fibrinopeptide A retained less than 25% of their initial immunoreactivity with R2 antiserum. It is concluded that the antigenic determinants of R2 immunoreactivity reside entirely within the COOH-terminal ten-residue sequence of fibrinopeptide A, and that Phe-8, Asp-7, and Arg-16 contribute significantly to R2 immunoreactivity. The R2 antigenic determinants appear to be significantly less accessible to reaction with antibody than the R33 determinants when the fibrinopeptide is attached to its parent alpha chain (Canfield et al., 1976). A possible mechanism for the sequestration is discussed.