A novel mutation of δ-aminolaevulinate dehydratase in a healthy child with 12% erythrocyte enzyme activity
A novel mutation of δ-aminolaevulinate dehydratase in a healthy child with 12% erythrocyte enzyme activity
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DOI：
10.1046/j.1365-2141.1999.01647.x
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发表时间：
1999-09-01
影响因子：
6.5
通讯作者：
Sassa, S
中科院分区：
文献类型：
--
作者：
Akagi, R;Yasui, Y;Sassa, S
对一个无症状女性ALAD缺陷症家系的ALAD缺陷基因进行了克隆、表达和表型研究。先证者通过新生儿ALAD筛查确定，红细胞ALAD活性为正常对照的12%。她是杂合子ALAD缺乏症，这是从她的父亲遗传。对克隆的ALADcDNA进行核苷酸序列分析，发现在同一等位基因上C-36突变为G，T-168突变为C。前者突变导致F12 L置换，而后者是沉默突变。所有ALAD活性降低的家庭成员都有相同的突变。突变ALAD cDNA在中国仓鼠卵巢细胞中的表达产生ALAD蛋白，而没有显着的酶活性。另外，编码F12 L置换的突变ALADcDNA在变性条件下的聚丙烯酰胺凝胶电泳中产生异常的迁移模式。这一发现可能反映了F12 L蛋白质的异常折叠，因为突变发生在酶N-末端臂的α 1螺旋上，其参与了亚基之间广泛的四级相互作用。这也是首次报道ALAD基因在无症状受试者中的突变。
Cloning, expression and phenotype studies of the defective gene for delta-aminolaevulinate dehydratase (ALAD) in a family with an asymptomatic girl who had ALAD deficiency were carried out. The proband was identified by neonatal ALAD screening, and had erythrocyte ALAD activity at 12% of the normal control. She was heterozygous for ALAD deficiency, which was inherited from her father. Nucleotide sequence analysis of the cloned ALAD cDNA revealed C-36 to G and T-168 to C mutations on the same allele. The former mutation resulted in F12L substitution, whereas the latter was a silent mutation. All family members who had decreased ALAD activity had the same mutation. Expression of the mutant ALAD cDNA in Chinese hamster ovary cells produced an ALAD protein without significant enzyme activity. Additionally, the mutant ALAD cDNA which encodes F12L substitution produced an aberrant migration pattern in polyacrylamide gel electrophoresis under denaturing conditions. This finding probably reflects an abnormal folding of the F12L protein, since the mutation occurred in the al helix of the N-terminal arm of the enzyme, which is involved in the extensive quaternary interactions among the subunits, This is also the first report of ALAD gene mutation in an asymptomatic subject.