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The actinobacterial cholesterol catabolic gene cluster contains a subset of genes that encode 13-oxidation enzymes with a putative role in sterol side chain degradation. We investigated the physiological roles of several genes, i.e., fadD17, fadD19, fadE26, fadE27, and ro04690DSM43269, by gene inactivation studies in mutant strain RG32 of Rhodococcus rhodochrous DSM43269. Mutant strain RG32 is devoid of 3-ketosteroid 9α-hydroxylase (KSH) activity and was constructed following the identification, cloning, and sequential inactivation of five kshA gene homologs in strain DSM43269. We show that mutant strain RG32 is fully blocked in steroid ring degradation but capable of selective sterol side chain degradation. Except for RG32ΔfadD19, none of the mutants constructed in RG32 revealed an aberrant phenotype on sterol side chain degradation compared to parent strain RG32. Deletion of fadD19 in strain RG32 completely blocked side chain degradation of C-24 branched sterols but interestingly not that of cholesterol. The additional inactivation of fadD17 in mutant RG32ΔfadD19 also did not affect cholesterol side chain degradation. Heterologously expressed FadD19DSM43269 nevertheless was active toward steroid-C26-oic acid substrates. Our data identified FadD19 as a steroid-coenzyme A (CoA) ligase with an essential in vivo role in the degradation of the side chains of C-24 branched-chain sterols. This paper reports the identification and characterization of a CoA ligase with an in vivo role in sterol side chain degradation. The high similarity (67%) between the FadD19DSM43269 and FadD19H37Rv enzymes further suggests that FadD19H37Rv has an in viva role in sterol metabolism of Mycobacterium tuberculosis H37Rv. [ABSTRACT FROM AUTHOR]

In a subset of papillary renal cell carcinomas a t(X;1)(p11;q21)chromosome translocation has repeatedly been reported.Positional cloning has demonstrated that,as a result of this translocation,the transcription factor TFE3 gene on the X-chromosome becomes fused to a novel gene,PRCC,on chro- mosome 1.Since as yet little is known about the function of PRCC,we sought to identify the mouse counterpart of the PRCC gene.Isolation and sequence analysis of a mouse Prcc cDNA revealed a high level of conservation between man and mouse,both at the nucleotide and protein level.As the human PRCC gene,the mouse Prcc gene is ubiquitously expressed.It shows low expression in all mouse fetal tissues examined.In addition,we identified a genomic cosmid clone containing the complete Prcc gene.The mouse Prcc gene consists of seven exons,all of which contain coding sequences.The small second exon,which was found to be located adjacent to the t(X;1) breakpoint in the human gene on chromosome 1,is also con- served between man and mouse.In mouse,Prcc is located on chromosome 3.These cDNA and genomic clones will be instru- mental in the creation of mouse models for a further elucida- tion of the function of PRCC. [ABSTRACT FROM AUTHOR]

Pond snails ( Lymnaea stagnalis (L.)) were treated with 2,2′-dichlorobiphenyl (DCB) or 4,4′-DCB, to examine the toxicokinetic profile of these compounds. Snails were treated orally with 210 μg 4,4′-DCB (impregnated on food) for 14 hr, or snails were injected with 50 μg of 2,2′-DCB or 4,4′-DCB in the foot. At different times after starting feeding or injection, tissues (albumen gland, digestive gland and digestive tube, central nervous system, remainder parts), hemolymph and faeces were analyzed for unchanged 2,2′- or 4,4′-DCB. The results showed that in case of oral administration of 4,4′-DCB after 144 hr, 97.5% of the dose was excreted unchanged in the faeces. During the first 48 hr 4,4′-DCB was found in all tissues. Thereafter, an exponential elimination was found (the rate constant of elimination (k) varied from 0.010-0.021 per hr, t from 33-60 hr and the apparent clearance from 0.02-0.3 g/hr for the different tissues). After injection, the compounds were found in all the above mentioned tissues, especially in the digestive gland. There was a clear difference between snails injected with 2,2′- and 4,4′-DCB. Firstly, k for 2,2′-DCB was higher (0.028 per hr vs 4,4′-DCB: 0.001 per hr). Secondly, 2,2′-DCB was lethal; 63% of the animals died after 72 hr. [ABSTRACT FROM AUTHOR]