Shulman M J, Collins C, Pennell N, Hozumi N
Eur J Immunol. 1987 Apr;17(4):549-54. doi: 10.1002/eji.1830170418.
We have isolated and analyzed the DNA encoding the mu heavy chain constant region of a mutant IgM which is defective in initiating complement-dependent cytolysis. By assaying the expression of mu genes which were constructed in vivo from mutant and normal gene segments, we have mapped the mutation into a 555-base pair segment. In this segment there is one nucleotide change, such that the mutant mu gene encodes serine rather than the normal proline at amino acid position 436 in the third constant domain. We have used site-directed mutagenesis to revert this mutation to the normal sequence and shown that this substitution results in the production of IgM with the normal phenotype.
我们已经分离并分析了编码一种突变型IgM的μ重链恒定区的DNA，该突变型IgM在启动补体依赖性细胞溶解方面存在缺陷。通过检测由突变和正常基因片段在体内构建的μ基因的表达，我们已将该突变定位到一个555碱基对的片段中。在这个片段中有一个核苷酸变化，使得突变型μ基因在第三个恒定结构域的氨基酸位置436处编码丝氨酸而非正常的脯氨酸。我们使用定点诱变将此突变恢复为正常序列，并表明这种取代导致产生具有正常表型 的IgM。
