Dufau M L, Minegishi T, Buczko E, Kitamura M, Delgado C, Namiki M
Molecular Endocrinology Section, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Ann N Y Acad Sci. 1989;564:57-76. doi: 10.1111/j.1749-6632.1989.tb25888.x.
A complete amino acid sequence for rat testis P-450 17 alpha was deduced from nucleotide analysis of a cDNA clone isolated from a rat Leydig cell library. This cDNA expressed in COS-1 cells both 17 alpha-hydroxylase and 17,20 lyase activities. Rat P-450 17 alpha exhibited significant similarity to the nucleotide and deduced amino acid sequences of the bovine and human P-450 17 alpha, particularly with the highly conserved regions and secondary structure. The rat P-450 17 alpha is anchored to the ER by two transmembrane regions: the N-terminal insertion peptide and the stop-transfer sequence. The C-terminal is associated with the ER by four hydrophobic clefts including the steroid-binding site. We have demonstrated a dual effect of hCG, causing early increases of Leydig cell P-450 17 alpha mRNA levels at low doses, while higher desensitizing doses caused marked subsequent reduction of mRNA levels. Our studies demonstrate that gonadotropin stimulation and desensitization of P-450 17 alpha dependent enzymes (17 alpha-hydroxylase/17,20 desmolase) in the adult rat testis and E2 induced desensitization in fetal Leydig cells are related to levels of P-450 17 alpha mRNA.
从大鼠睾丸间质细胞文库中分离得到的一个cDNA克隆的核苷酸分析结果推导得出大鼠睾丸P-450 17α的完整氨基酸序列。该cDNA在COS-1细胞中表达出17α-羟化酶和17,20-裂解酶活性。大鼠P-450 17α与牛和人P-450 17α的核苷酸序列和推导的氨基酸序列表现出显著相似性，特别是在高度保守区域和二级结构方面。大鼠P-450 17α通过两个跨膜区域锚定在内质网上：N端插入肽和终止转移序列。C端通过包括类固醇结合位点在内的四个疏水裂隙与内质网相关联。我们已经证明了hCG的双重作用，低剂量时会导致睾丸间质细胞P-450 17α mRNA水平早期升高，而高剂量脱敏时会导致随后mRNA水平显著降低。我们的研究表明，成年大鼠睾丸中促性腺激素对P-450 17α依赖性酶（17α-羟化酶/17,20-裂解酶）的刺激和脱敏作用，以及胎儿睾丸间质细胞中E2诱导的脱敏作用与P-450 17α mRNA水平有关。
