Department of Botany, King's Buildings, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JH, UK.
EMBO J. 1984 Sep;3(9):2107-13. doi: 10.1002/j.1460-2075.1984.tb02098.x.
The apocytochrome b (COB) gene has been isolated from maize (Zea mays L.) mitochondrial DNA. Sequence analysis reveals that the coding region of the gene is 1164 bp long and, in contrast with the homologous gene from yeast, does not contain introns or TGA (Trp) codons. The predicted polypeptide encoded by the gene has a mol. wt. of 42 868 daltons, and shows 48% amino acid sequence homology with the corresponding yeast and mammalian polypeptides. Hydropathic profiles of the polypeptide indicate the presence of nine, membrane spanning hydrophobic domains suggesting that it is organised in the inner mitochondrial membrane in a similar fashion to that proposed for apocytochrome b in other organisms. The COB gene is preceded by a sequence 5' -AGTTGTCA-3' which may act as a ribosome binding site in the mRNA since: (i) it shows 67.5% complementarity with an octanucleotide at the 3' end of the maize mitochondrial 18S rRNA, located in a position homologous to that of the Escherichia coli Shine and Dalgarno sequence, and (ii) a similar sequence precedes several other plant mitochondrial genes at a distance of 15-20 nucleotides from the ATG initiation codon. RNA transcript analysis shows that the gene is transcribed in a complex manner with the presumed mature mRNA ( 2.25 kb) probably being derived by sequential processing from a larger primary transcript.
从玉米（Zea mays L.）线粒体 DNA 中分离出了细胞色素 b（COB）基因。序列分析表明，该基因的编码区长 1164bp，与酵母同源基因不同，它不包含内含子或 TGA（色氨酸）密码子。该基因编码的预测多肽分子量为 42868 道尔顿，与相应的酵母和哺乳动物多肽具有 48%的氨基酸序列同源性。多肽的疏水性图谱表明，存在 9 个跨膜疏水区，表明它在类似于其他生物的细胞色素 b 在内膜中的方式组织。COB 基因之前有一个 5' -AGTTGTCA-3'序列，它可能在 mRNA 中作为核糖体结合位点，因为：(i) 它与位于大肠杆菌 Shine 和 Dalgarno 序列同源位置的玉米线粒体 18S rRNA 3'端的一个八核苷酸具有 67.5%的互补性，和 (ii) 类似的序列在距离 ATG 起始密码子 15-20 个核苷酸的距离处，出现在其他几个植物线粒体基因之前。RNA 转录分析表明，该基因以复杂的方式转录，假定的成熟 mRNA（2.25kb）可能是通过从较大的初级转录本中连续加工而来的。
