Cabrera J E, Panzetta-Dutari G, Pruneda J L, Genti-Raimondi S
Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Argentina.
J Steroid Biochem Mol Biol. 1997 Sep-Oct;63(1-3):91-8. doi: 10.1016/s0960-0760(97)00078-2.
Comamonas testosteroni can grow on a variety of steroid compounds as the sole carbon and energy source. In a previous study, we cloned and sequenced the testosterone-inducible betahsd gene from C. testosteroni (Genti-Raimondi, S., Tolmasky, M., Patrito, L., Flury, A. and Actis, L., Molecular cloning and expression of the beta-hydroxysteroid dehydrogenase gene from Pseudomonas testosteroni. Gene, 1991, 105, 43-49.). Herein we report the cloning and characterization of another steroid-inducible gene (stdC), located 2400 bp upstream of betahsd. Nucleotide sequencing of a region encompassing the stdC gene revealed an open reading frame 546 bp long including the stop codon TGA with significant similarity to the orf4, orf1 and orf4 of unknown function described in the polyhydroxyalkanoic acid (PHA) cluster of Chromatium vinosum, Rhizobium meliloti and Thiocystis violacea, respectively. The aminoacid sequence deduced from the nucleotide sequence predicts a putative protein of 181 amino acids with a molecular weight of 20715 Da. Northern blot experiments indicate that the stdC gene was transcribed as a monocistronic mRNA with an apparent molecular size of 670 nt. The stdC transcript was abundant in C. testosteroni cells grown with different steroid carbon sources harvested in the exponential phase and was found to be under catabolite repression.
睾丸酮丛毛单胞菌能够以多种类固醇化合物作为唯一的碳源和能源进行生长。在之前的一项研究中，我们从睾丸酮丛毛单胞菌中克隆并测序了睾丸酮诱导型β-羟类固醇脱氢酶基因（Genti-Raimondi, S., Tolmasky, M., Patrito, L., Flury, A. 和 Actis, L.，睾丸酮假单胞菌β-羟类固醇脱氢酶基因的分子克隆与表达。《基因》，1991年，第105卷，第43 - 49页）。在此，我们报告另一个类固醇诱导型基因（stdC）的克隆与特性分析，该基因位于betahsd上游2400 bp处。对包含stdC基因的一个区域进行核苷酸测序，发现一个546 bp长的开放阅读框，包括终止密码子TGA，分别与嗜硫红假单胞菌、苜蓿根瘤菌和紫色硫囊菌的聚羟基脂肪酸酯（PHA）簇中描述的功能未知的orf4、orf1和orf4具有显著相似性。从核苷酸序列推导的氨基酸序列预测出一个由181个氨基酸组成的推定蛋白质，分子量为20715 Da。Northern杂交实验表明，stdC基因转录为一个单顺反子mRNA，表观分子大小为670 nt。stdC转录本在指数生长期收获的、以不同类固醇碳源生长的睾丸酮丛毛单胞菌细胞中丰富，并且发现其受到分解代谢物阻遏。
