A NEW COMAMONAS-TESTOSTERONI STEROID-INDUCIBLE GENE - CLONING AND SEQUENCE-ANALYSIS

Comamonas testosteroni can grow on a variety of steroid compounds as t he sole carbon and energy source. In a previous study, we cloned and s equenced the testosterone-inducible beta hsd gene from C. testosteroni (Genti-Raimondi, S., Tolmasky, M., Patrito, L., Flury, A. and Actis, L., Molecular cloning and expression of the B-hydroxysteroid dehydroge nase gene from Pseudomonas testosteroni. Gene, 1991, 105, 43-49.). Her ein we report the cloning and characterization of another steroid-indu cible gene (stdC), located 2400 bp upstream of beta hsd. Nucleotide se quencing of a region encompassing the stdC gene revealed an open readi ng frame 546 bp long including the stop codon TGA with significant sim ilarity to the orf4, orf1 and orf4 of unknown function described in th e polyhydroxyalkanoic acid (PHA) cluster of Chromatium vinosum, Rhizob ium meliloti and Thiocystis violacea, respectively. The aminoacid sequ ence deduced from the nucleotide sequence predicts a putative protein of 181 amino acids with a molecular weight of 20 715 Da. Northern blot experiments indicate that the stdC gene was transcribed as a monocist ronic mRNA with an apparent molecular size of 670 nt. The stdC transcr ipt 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. (C) 1997 Elsevier Science Ltd. All right s reserved.