Kagimoto M, Kagimoto K, Simpson E R, Waterman M R
Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas 75235.
J Biol Chem. 1988 Jun 25;263(18):8925-8.
The 5'-end of the bovine adrenodoxin gene contains unique structural characteristics. Exons 1 and 2 appear to encode different presequences for this mitochondrial precursor protein. However, exon 1 contains a stop codon (TAA) in place of amino acid 15. Thus, while two species of bovine adrenodoxin mRNA arise from a single gene, only the abundant mRNA species (90%) is translated into the adrenodoxin precursor which contains the presequence encoded by exon 2. The minor mRNA species (10%) contains the sequence encoded by exon 1 and cannot be translated into an adrenodoxin precursor. Presumably the sequence within exon 2 is removed from this minor mRNA species by alternative splicing. Furthermore, the initiation of transcription of the major adrenodoxin mRNA (exon 2) lies within intron 1 of this unusual gene, while that for the other mRNA (exon 1) lies in the 5'-flanking region. Thus, the adrenodoxin gene is the first example of a gene encoding a mitochondrial protein which falls into the category of genes having alternate promoters utilizing a pattern of alternative splicing.
牛肾上腺皮质铁氧化还原蛋白基因的5'端具有独特的结构特征。外显子1和2似乎为这种线粒体前体蛋白编码不同的前导序列。然而，外显子1在第15个氨基酸位置含有一个终止密码子（TAA）。因此，虽然两种牛肾上腺皮质铁氧化还原蛋白mRNA来自单个基因，但只有丰富的mRNA种类（90%）被翻译成肾上腺皮质铁氧化还原蛋白前体，该前体包含由外显子2编码的前导序列。少量的mRNA种类（10%）包含由外显子1编码的序列，不能被翻译成肾上腺皮质铁氧化还原蛋白前体。推测外显子2内的序列通过可变剪接从这种少量的mRNA种类中去除。此外，主要的肾上腺皮质铁氧化还原蛋白mRNA（外显子2）的转录起始位于这个不寻常基因的内含子1内，而另一种mRNA（外显子1）的转录起始位于5'侧翼区域。因此，肾上腺皮质铁氧化还原蛋白基因是编码线粒体蛋白的基因的第一个例子，该基因属于具有利用可变剪接模式的交替启动子的基因类别。
