Westlind A, Malmebo S, Johansson I, Otter C, Andersson T B, Ingelman-Sundberg M, Oscarson M
Division of Molecular Toxicology, IMM, Karolinska Institutet, Stockholm, SE-171 77, Sweden.
Biochem Biophys Res Commun. 2001 Mar;281(5):1349-55. doi: 10.1006/bbrc.2001.4505.
On the basis of the detection of an expressed sequence tag ('EST') similar to the human cytochrome P450 3A4 cDNA, we have identified a novel member of the human cytochrome P450 3A subfamily. The coding region is 1512-bp long and shares 84, 83, and 82% sequence identity on the cDNA level with CYP3A4, 3A5, and 3A7, respectively, with a corresponding amino acid identity of 76, 76, and 71%. Quantitative real time based mRNA analysis revealed CYP3A43 expression levels at about 0.1% of CYP3A4 and 2% of CYP3A5 in the liver, with significant expression in 70% of the livers examined. Gene specific PCR of cDNA from extrahepatic tissues showed, with the exception of the testis, only low levels of CYP3A43 expression. The CYP3A43 cDNA was heterologously expressed in yeast, COS-1 cells, mouse hepatic H2.35 cells and in human embryonic kidney (HEK) 293 cells, but in contrast to CYP3A4 which was formed in all cell types, no detectable CYP3A43 protein was produced. This indicates a nonfunctional protein or specific conditions required for proper folding. It is concluded that CYP3A43 mRNA is expressed mainly in liver and testis and that the protein would not contribute significantly to human drug metabolism.
基于对一个与人类细胞色素P450 3A4 cDNA相似的表达序列标签（'EST'）的检测，我们鉴定出了人类细胞色素P450 3A亚家族的一个新成员。其编码区长度为1512 bp，在cDNA水平上与CYP3A4、3A5和3A7的序列同一性分别为84%、83%和82%，相应的氨基酸同一性为76%、76%和71%。基于定量实时的mRNA分析显示，肝脏中CYP3A43的表达水平约为CYP3A4的0.1%和CYP3A5的2%，在所检测的70%的肝脏中有显著表达。来自肝外组织的cDNA的基因特异性PCR显示，除睾丸外，CYP3A43仅表达低水平。CYP3A43 cDNA在酵母、COS-1细胞、小鼠肝脏H2.35细胞和人胚肾（HEK）293细胞中进行了异源表达，但与在所有细胞类型中均能形成的CYP3A4不同，未检测到CYP3A43蛋白的产生。这表明该蛋白无功能或需要特定条件才能正确折叠。结论是CYP3A43 mRNA主要在肝脏和睾丸中表达，且该蛋白对人类药物代谢的贡献不大。
