Cunningham M, Beachey E H
J Immunol. 1975 Oct;115(4):1002-6.
Electrofucusing of an alkaline extract of type 24 streptococcal M protein yielded an antigenic fraction that was type specific and apparently homogeneous. The haptenic nature of this fraction was suggested by its inability to precipitate type-specific antiserum or to induce opsonic antibodies in rabbits, despite its ability to strongly inhibit opsonization of homologous-type streptococci by M antibody. The fraction migrated as a single band upon electrophoresis in sodium dodecyl sulfate (SDS) acrylamide gel. The mobility of the protein band was consistent with a molecular weight of 36,500 daltons. In some experiments using larger quantities of protein, a second faint protein band with an average molecular weight of 70,000 was observed, suggesting the presence of dimers of the 36,500-dalton protein. Amino acid analysis showed the predominant amino acid to be glycine followed by aspartic acid and glutamic acid. Moreover, this M protein fraction was free of non-type-specific immunotoxic properties in guinea pigs and in man. Although apparently not immunogenic, this nontoxic fraction may provide a useful tool to study the relationship of the type-specific protective moiety to potentially harmful "impurities" in M protein vaccines.
对24型链球菌M蛋白的碱性提取物进行等电聚焦，得到了一个具有型特异性且明显均一的抗原组分。尽管该组分能够强烈抑制M抗体对同源型链球菌的调理作用，但其无法沉淀型特异性抗血清或在兔体内诱导调理抗体，这表明了该组分的半抗原性质。在十二烷基硫酸钠（SDS）聚丙烯酰胺凝胶中进行电泳时，该组分迁移为单一的条带。蛋白质条带的迁移率与分子量36,500道尔顿一致。在一些使用大量蛋白质的实验中，观察到了第二条微弱的蛋白质条带，其平均分子量为70,000，这表明存在36,500道尔顿蛋白质的二聚体。氨基酸分析表明，主要氨基酸为甘氨酸，其次是天冬氨酸和谷氨酸。此外，该M蛋白组分在豚鼠和人体中没有非型特异性免疫毒性特性。尽管该无毒组分显然没有免疫原性，但它可能为研究M蛋白疫苗中型特异性保护部分与潜在有害“杂质”之间的关系提供一个有用的工具。
