2,3-Dihydroxypropane-1-sulfonate (DHPS) is a widespread intermediate in plant and algal transformations of sulfoquinovose (SQ) from the plant sulfolipid sulfoquinovosyl diacylglycerol. Further, DHPS is recovered quantitatively during bacterial degradation of SQ by Klebsiella sp. strain ABR11. DHPS is also a putative precursor of sulfolactate in e.g. Ruegeria pomeroyi DSS-3. A bioinformatic approach indicated that some 28 organisms with sequenced genomes might degrade DHPS inducibly via sulfolactate, with three different desulfonative enzymes involved in its degradation in different organisms. The hypothesis for Cupriavidus pinatubonensis JMP134 (formerly Ralstonia eutropha) involved a seven-gene cluster (Reut_C6093-C6087) comprising a LacI-type transcriptional regulator, HpsR, a major facilitator superfamily uptake system, HpsU, three NAD(P) + -coupled DHPS dehydrogenases, HpsNOP, and (R)-sulfolactate sulfo-lyase . Representative organisms were found to grow with DHPS and release sulfate. C. pinatubonensis JMP134 was found to express at least one NAD(P) + -coupled DHPS dehydrogenase inducibly, and three different peaks of activity were separated by anion-exchange chromatography. Protein bands (SDS-PAGE) were subjected to peptide-mass fingerprinting, which identified the corresponding genes (hpsNOP). Purified HpsN converted DHPS to sulfolactate. Reverse-transcription PCR confirmed that hpsNOUP were transcribed inducibly in strain JMP134, and that hpsKLM and hpsNOP were transcribed in strain ISM. DHPS degradation is widespread and diverse, implying that DHPS is common in marine and terrestrial environments.

The high substrate specificity of DNA-dependent DNA polymerases is essential for the stability of the genome as well as many biotechnological applications. [1] The discrimination between ribo-and deoxyribonucleotides and between RNA and DNA, particularly in cells, is fundamental since the concentration of ribo moieties by far exceeds that of deoxyribo analogues. Although the selection mechanisms for the incorporation of nucleotides have been investigated intensively for DNA and RNA polymerases, [2] much less is known on how DNA-dependent DNA polymerases discriminate between the different nucleic acid templates (DNA versus RNA). Some viral DNA polymerases (e.g. reverse transcriptases) can utilize both DNA and RNA as a template for nucleic acid synthesis. Crystal-structure analysis of these enzymes, complexed either to an RNA or DNA template, have contributed significantly to our understanding of this process. [3] However, similar structural data of DNA-dependent DNA polymerases that have a poor propensity to process RNA templates are lacking, presumably because the crystallization is hampered by the formation of unstable complexes that leads to structural heterogeneity.Structure analysis of KlenTaq DNA polymerase, a shortened form of Thermus aquaticus DNA polymerase, has added significant contributions to the understanding of how DNA polymerases recognize the cognate substrate, [4] process abasic sites, [5] and non-natural nucleotides. [4d-g] Since our attempts to obtain suitable crystals of KlenTaq complexed to RNA failed, we set out to engineer the enzyme in such a way that it is capable of processing an RNA template more efficiently, which might result in improved crystallization properties. Indeed, we were able to obtain a significantly improved KlenTaq variant from which we obtained structural insights into a DNA-dependent DNA polymerase while processing RNA as a template for the first time. Furthermore, the generated KlenTaq variant turned out to be a thermostable DNA polymerase with significant reverse transcriptase activity, thus resulting in it being a valuable tool for crucial applications in clinical diagnostics and molecular biology, such as transcriptome analysis as well as the detection of pathogens and disease-specific markers.For the generation of an improved enzyme variant the mutation sites of two KlenTaq (KTq) variants M1 (L322M, L459M, S515R, I638F, S739G, E773G) [6] and M747K [7] were recombined by DNA shuffling. Both variants, M1 and M747K, were reported to possess either some reverse transcriptase activity or an expanded substrate spectrum. DNA shuffling was employed since the M1 variant, previously evolved in error-prone PCR, comprises six mutations distributed over the enzyme scaffold, but the individual contributions of the mutations are unknown. We generated a library of 1570 clones to obtain high coverage of all mutation combinations (as described in the Supporting Information). Proteins were expressed in 96-well plates and, after lysis and heat denaturation of the host proteins, use...

Data from the genome sequence of the aerobic, marine bacterium Roseovarius nubinhibens ISM were interpreted such that 3-sulfolactate would be degraded as a sole source of carbon and energy for growth via a novel bifurcated pathway including two known desulfonative enzymes, sulfoacetaldehyde acetyltransferase (EC 2.3.3.15) (Xsc) and cysteate sulfo-lyase (EC 4.4.1.25) (CuyA). Strain ISM utilized sulfolactate quantitatively with stoichiometric excretion of the sulfonate sulfur as sulfate. A combination of enzyme assays, analytical chemistry, enzyme purification, peptide mass fingerprinting, and reverse transcription-PCR data supported the presence of an inducible, tripartite sulfolactate uptake system (SlcHFG), and a membrane-bound sulfolactate dehydrogenase (SlcD) which generated 3-sulfopyruvate, the point of bifurcation. 3-Sulfopyruvate was in part decarboxylated by 3-sulfopyruvate decarboxylase (EC 4.1.1.79) (ComDE), which was purified. The sulfoacetaldehyde that was formed was desulfonated by Xsc, which was identified, and the acetyl phosphate was converted to acetyl-coenzyme A by phosphate acetyltransferase (Pta). The other portion of the 3-sulfopyruvate was transaminated to (S)-cysteate, which was desulfonated by CuyA, which was identified. The sulfite that was formed was presumably exported by CuyZ (TC 9.B.7.1.1 in the transport classification system), and a periplasmic sulfite dehydrogenase is presumed. Bioinformatic analyses indicated that transporter SlcHFG is rare but that SlcD is involved in three different combinations of pathways, the bifurcated pathway shown here, via CuyA alone, and via Xsc alone. This novel pathway involves ComDE in biodegradation, whereas it was discovered in the biosynthesis of coenzyme M. The different pathways of desulfonation of sulfolactate presumably represent final steps in the biodegradation of sulfoquinovose (and exudates derived from it) in marine and aquatic environments.Sulfolactate (Fig. 1A) is a widespread natural product, which contains the stable C-SO 3 Ϫ bond. The compound is known to be (i) a component (5% of dry weight) of bacterial endospores (5), (ii) an intermediate in the biosynthesis of coenzyme M in archaea (55), (iii) in equilibrium with (S)-cysteate in mammals (54), (iv) involved in the metabolism of sulfoquinovose (6-deoxy-6-sulfo-D-glucopyranose, the polar moiety of the plant sulfolipid) in plants and algae (e.g., see reference 48), and (v) an intermediate in the bacterial degradation of sulfoquinovose (44).Research on the biodegradation of organosulfonates has concentrated on compounds containing one to four carbon atoms (C 1 , C 2 , C 3 , or C 4 sulfonates), because where appropriate, larger molecules all seemed to be processed via one of the five desulfonative reactions that have been elucidated. Pathways from (i) sulfoquinovose yield, e.g., sulfoacetate or sulfolactate and 2,3-dihydroxy-1-sulfopropane (36, 44), (ii) taurocholate and N-acetyltaurine yield taurine (37, 43), and (iii) N-methyltaurine yield sulfoacetaldehyde (52). The five desulfonatio...

Homotaurine (3-aminopropanesulfonate), a natural product and an analogue of GABA (4-aminobutyrate), was found to be a sole source of nitrogen for Cupriavidus necator (Ralstonia eutropha) H16, whose genome sequence is known. Homotaurine nitrogen was assimilated into cell material, and the quantitative fate of the organosulfonate was sulfopropanoate, which was recovered in the growth medium. The first scalar reaction was shown to be inducible homotaurine:2-oxoglutarate aminotransferase, which released 3-sulfopropanal from homotaurine. This aminotransferase was purified to homogeneity and characterized. Peptide mass fingerprinting yielded locus tag H16_B0981, which was annotated gabT, for GABA transaminase (EC 2.6.1.19). Inducible, NAD(P) ؉ -coupled 3-sulfopropanal dehydrogenase, which yielded 3-sulfopropanoate from 3-sulfopropanal, was also purified and characterized. Peptide mass fingerprinting yielded locus tag H16_B0982, which was annotated gabD1, for succinate-semialdehyde dehydrogenase (EC 1.2.1.16). GabT and GabD1 were each induced during growth with GABA, and cotranscription of gabTD was observed. In other organisms, regulator GabC or GabR is encoded contiguous with gabTD: candidate GabR was found in strain H16 and in many other organisms. An orthologue of the GABA permease (GabP), established in Escherichia coli, is present at H16_B1890, and it was transcribed constitutively. We presume that GabRPTD are responsible for the inducible metabolism of homotaurine to intracellular 3-sulfopropanoate. The nature of the exporter of this highly charged compound was unclear until we realized from the sodium dodecyl sulfate-polyacrylamide gel electrophoresis data that sulfoacetaldehyde acetyltransferase (EC 2.3.3.15; H16_B1872) was strongly induced during growth with homotaurine and inferred that the sulfite exporter encoded at the end of the gene cluster (H16_B1874) has a broad substrate range that includes 3-sulfopropanoate.

The naturally occurring sulfonate N-acetyltaurine was synthesized chemically and its identity was confirmed. Aerobic enrichment cultures for bacteria able to utilize N-acetyltaurine as sole source of fixed nitrogen or as sole source of carbon were successful. One representative isolate, strain NAT, which was identified as a strain of Delftia acidovorans, grew with N-acetyltaurine as carbon source and excreted stoichiometric amounts of sulfate and ammonium. Inducible enzyme activities were measured in crude extracts of this organism to elucidate the degradative pathway. Cleavage of N-acetyltaurine by a highly active amidase yielded acetate and taurine. The latter was oxidatively deaminated by taurine dehydrogenase to ammonium and sulfoacetaldehyde. This key intermediate of sulfonate catabolism was desulfonated by the known reaction of sulfoacetaldehyde acetyltransferase to sulfite and acetyl phosphate, which was further degraded to enter central metabolism. A degradative pathway including transport functions is proposed.