Levine M, Movafagh B F
Mol Immunol. 1986 Mar;23(3):255-61. doi: 10.1016/0161-5890(86)90051-9.
The specificity of a frequently-occurring precipitin response to soluble antigens from cell-walls and culture filtrates of A. viscosus ATCC 19246 was examined. After precipitation with isopropanol (50-75% v/v), antigen fractions of different charge and molecular weight were isolated by ion exchange and gel filtration. When heated in mineral acid or alkali above 0.15 M, each of the purified antigens lost precipitating activity, but now inhibited the precipitin reaction between serum and exogenous unheated antigen. The inhibitor was isolated over Biogel P30 and characterized as a peptide fragment (mol. wt about 2 kd) containing approximately 50 moles of ornithine and 6-12 moles, respectively, of aspartate, serine, threonine, glutamate, glycine, alanine and histidine per 100 moles amino acids. The inhibitor was totally destroyed by heating for 1.0 hr in 2.0 M HCl. Variability in the number of fragments and differences in the non-antigenic portions probably accounted for the complexity of the antigens. Ornithine, putrescine, N-acetyl putrescine and various sugars had little or no effect on the precipitin reaction with intact antigen at high concentrations (200 mM), whereas the fragment inhibited completely at 0.4 mM. This indicates that neither ornithine nor its side-chain amides are exclusively recognized by antibody. However, ornithine may be part of a larger sequence and/or important in forming the configuration recognized by the human antibodies.
对粘性放线菌ATCC 19246细胞壁和培养滤液中的可溶性抗原频繁出现的沉淀素反应的特异性进行了研究。用异丙醇（50 - 75% v/v）沉淀后，通过离子交换和凝胶过滤分离出不同电荷和分子量的抗原组分。当在0.15 M以上的无机酸或碱中加热时，每种纯化抗原均失去沉淀活性，但此时会抑制血清与未加热的外源性抗原之间的沉淀素反应。该抑制剂通过Biogel P30分离得到，其特征为一种肽片段（分子量约2 kd），每100摩尔氨基酸中分别含有约50摩尔鸟氨酸以及6 - 12摩尔的天冬氨酸、丝氨酸、苏氨酸、谷氨酸、甘氨酸、丙氨酸和组氨酸。该抑制剂在2.0 M HCl中加热1.0小时后完全被破坏。片段数量的变异性以及非抗原部分的差异可能解释了抗原的复杂性。高浓度（200 mM）时，鸟氨酸、腐胺、N - 乙酰腐胺和各种糖类对与完整抗原的沉淀素反应几乎没有影响，而该片段在0.4 mM时完全抑制反应。这表明抗体并非仅识别鸟氨酸及其侧链酰胺。然而，鸟氨酸可能是更大序列的一部分和/或在形成被人类抗体识别的构象中起重要作用。
