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Some properties of the rhodanese system of Thiobacillus denitrificans.

ABSTRACT: 1. Rhodanese has been extracted from Thiobacillus denitrificans by ultrasonic disintegration of the cells. 2. Studies with Sephadex columns have shown that the enzyme aggregates, forming a tetramer. 3. The molecular weights of the monomer and of an enzymically active sub-unit one-quarter this size have been determined by gel filtration. 4. Higher-molecular-weight forms of rhodanese are broken down by mercaptoethanol to enzymically active fragments of mol.wt. 7000 and 2000 respectively. 5. It is suggested that these fragments are linked in vivo via disulphide bridges to form the monomer, which can then aggregate via further disulphide links. 6. The fragment of mol.wt. 7000 has been obtained in a substantially pure state. 7. Both disulphide and thiol groups are necessary for enzyme activity. 8. Similarities and differences existing between bacterial rhodanese, mammalian rhodanese and beta-mercaptopyruvate sulphurtransferase are discussed.

SUBMITTER: Bowen TJ

PROVIDER: S-EPMC1264741 | biostudies-other | 1965 Dec

REPOSITORIES: biostudies-other

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Project description:Beller, H. R., T. E. Letain, A. Chakicherla, S. R. Kane, T. C. Legler, and M. A. Coleman. 2006. Whole-genome transcriptional analysis of chemolithoautotrophic thiosulfate oxidation by Thiobacillus denitrificans under aerobic vs. denitrifying conditions. Journal of Bacteriology 188:7005-7015. Thiobacillus denitrificans is one of the few known obligate chemolithoautotrophic bacteria capable of energetically coupling thiosulfate oxidation to denitrification as well as aerobic respiration. As very little is known about the differential expression of genes associated with key chemolithoautotrophic functions (such as sulfur-compound oxidation and CO2 fixation) under aerobic versus denitrifying conditions, we conducted whole-genome, cDNA microarray studies to explore this topic systematically. The microarrays identified 277 genes (approximately ten percent of the genome) as differentially expressed using Robust Multi-array Average statistical analysis and a 2-fold cutoff. Genes upregulated (ca. 6- to 150-fold) under aerobic conditions included a cluster of genes associated with iron acquisition (e.g., siderophore-related genes), a cluster of cytochrome cbb3 oxidase genes, cbbL and cbbS (encoding the large and small subunits of form I ribulose 1,5-bisphosphate carboxylase/oxygenase, or RubisCO), and multiple molecular chaperone genes. Genes upregulated (ca. 4- to 95-fold) under denitrifying conditions included nar, nir, and nor genes (associated respectively with nitrate reductase, nitrite reductase, and nitric oxide reductase, which catalyze successive steps of denitrification), cbbM (encoding form II RubisCO), and genes involved with sulfur-compound oxidation (including two physically separated but highly similar copies of sulfide:quinone oxidoreductase and of dsrC, associated with dissimilatory sulfite reductase). Among genes associated with denitrification, relative expression levels (i.e., degree of upregulation with nitrate) tended to decrease in the order nar > nir > nor > nos. Reverse transcription, quantitative PCR analysis was used to validate these trends. Keywords: bacterial metabolism

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Some properties of the rhodanese system of Thiobacillus denitrificans.

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