黑腹果蝇杂合体中ADH杂二聚体的形成

研究了醇脱氢酶基因 (Adh)诱变体与正常基因相互作用后的部分显性现象 .所有 8个由乙基亚硝基尿素 (ENU)和 1个 X-射线诱变体仅为单碱基置换体 ,其余 3个 X-射线诱变体则为 9～2 1个碱基的缺失体 .这 1 2个诱变体 (除 1个外 )都能产生可测的突变肽 ,其中 7个不能与正常肽形成二聚体 ,杂合体酶活性约为正常纯合体的 1 /2 ;另 4个形成二聚体 .形成二聚体突变基因产物中所有氨基酸突变均发生在肽链 1 82～ 1 94氨基酸区域 ,可见该区域对于二聚化不是必需的 ,该序列可能是重要的催化表面功能区

ADH Heterodimer Formation in Heterozygotes between Induced Null Alleles and Normal Alleles in Drosophila melanogester

To study the mechanisms for dominance of phenotype, 8 ENU and 4 X ray induced mutations at the alchohol dehydrogenase(Adh) locus were analyzed for the partial dominance in their interaction with normal alleles. All ENU mutations and one of the X ray mutations are single base substitutions; the other 3 X ray mutations are 9~21 base deletions. All but one of the 12 mutant alleles were selected for this study because they produce a detectable mutant polypeptide, but 7 of the 11 producing a peptide could not form dimers with the normal peptide and the enzyme activity of heterozygotes is about half that of normal homozygotes. Four mutations form the dimers with a decreased catalytic efficiency. All amino acid changes in mutant genes that form dimers are located between 182 and 194, so this region is not critical for dimerization. It may, however, be an important surface domain for catalyzation.