Cloning and tissue distribution of a novel human cytochrome p450 of the CYP3A subfamily, CYP3A43.
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.
Division of Molecular Toxicology, IMM, Karolinska Institutet, Stockholm, SE-171 77, Sweden.
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A
Westlind
S
S
Malmebo
I
I
Johansson
C
C
Otter
T B
TB
Andersson
M
M
Ingelman-Sundberg
M
M
Oscarson
D000595:Amino Acid Sequence; D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D001483:Base Sequence; D019556:COS Cells; D002460:Cell Line; D003001:Cloning, Molecular; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000235:genetics*; D020224:Expressed Sequence Tags; D006801:Humans; D008099:Liver / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000096:biosynthesis / Q000235:genetics; D008969:Molecular Sequence Data; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis / Q000235:genetics*; D020033:Protein Isoforms / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014162:Transfection; D014407:Tumor Cells, Cultured
D020033:Protein Isoforms; D012333:RNA, Messenger; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C104464:CYP3A protein, human; C422408:CYP3A43 protein, human; C510164:CYP3A5 protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D010089:Oxidoreductases, N-Demethylating