The Escherichia coli cysG gene encodes S-adenosylmethionine-dependent uroporphyrinogen III methylase.
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ABSTRACT:
SUBMITTER: Warren MJ
PROVIDER: S-EPMC1133693 | biostudies-other | 1990 Feb
REPOSITORIES: biostudies-other
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Project description:The C-terminus of the Escherichia coli CysG protein, consisting of amino acids 202-457, was expressed as a recombinant protein using gene dissection methodology. Analysis of the activity of this truncated protein, termed CysGA, revealed that it was able to methylate uroporphyrinogen III in the same S-adenosyl-L-methionine (SAM)-dependent manner as the complete CysG protein. However, this truncated protein was not able to complement E. coli cysG cells, thereby suggesting that the first 201 amino acids of the CysG protein had an enzymic activity associated with the conversion of dihydrosirohydrochlorin into sirohaem. Analysis of the N-terminus of the CysG protein revealed the presence of a putative pyridine dinucleotide binding site. When the purified CysG protein was incubated with NADP+, uroporphyrinogen III and SAM the enzyme was found to catalyse a coenzyme-mediated dehydrogenation to form sirohydrochlorin. The CysGA protein on the other hand showed no such coenzyme-dependent activity. Analysis of the porphyrinoid material isolated from strains harbouring plasmids containing the complete and truncated cysG genes suggested that the CysG protein was also involved in ferrochelation. The evidence presented in this paper suggests that the CysG protein is a multifunctional protein involved in SAM-dependent methylation, pyridine dinucleotide dependent dehydrogenation and ferrochelation.
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Project description:The uroporphyrinogen III synthase (UROS) enzyme (also known as hydroxymethylbilane hydrolyase) catalyzes the cyclization of hydroxymethylbilane to uroporphyrinogen III during heme biosynthesis. A deficiency of this enzyme is associated with the very rare Gunther's disease or congenital erythropoietic porphyria, an autosomal recessive inborn error of metabolism. The current study investigated the possible role of UROS (Homo sapiens [EC: 4.2.1.75; 265 aa; 1371 bp mRNA; Entrez Pubmed ref NP_000366.1, NM_000375.2]) in evolution by studying the phylogenetic relationship and divergence of this gene using computational methods. The UROS protein sequences from various taxa were retrieved from GenBank database and were compared using Clustal-W (multiple sequence alignment) with defaults and a first-pass phylogenetic tree was built using neighbor-joining method as in DELTA BLAST 2.2.27+ version. A total of 163 BLAST hits were found for the uroporphyrinogen III synthase query sequence and these hits showed putative conserved domain, HemD superfamily (as on 14(th) Nov 2012). We then narrowed down the search by manually deleting the proteins which were not UROS sequences and sequences belonging to phyla other than Chordata were deleted. A repeat phylogenetic analysis of 39 taxa was performed using PhyML and TreeDyn software to confirm that UROS is a highly conserved protein with approximately 85% conserved sequences in almost all chordate taxons emphasizing its importance in heme synthesis.
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Project description:S-adenosylmethionine (AdoMet) synthetase (EC 2.5.1.6) is the enzyme that catalyzes the synthesis of AdoMet, a molecule important for all cellular organisms. We have cloned and characterized an AdoMet synthetase gene (sam1) from Pneumocystis spp. This gene was transcribed primarily as an approximately 1.3-kb mRNA which encodes a protein containing 381 amino acids in P. carinii or P. murina and 382 amino acids in P. jirovecii. sam1 was also transcribed as part of an apparent polycistronic transcript of approximately 5.6 kb, together with a putative chromatin remodeling protein homologous to Saccharomyces cerevisiae, CHD1. Recombinant Sam1, when expressed in Escherichia coli, showed functional enzyme activity. Immunoprecipitation and confocal immunofluorescence analysis using an antipeptide antibody showed that this enzyme is expressed in P. murina. Thus, Pneumocystis, like other organisms, can synthesize its own AdoMet and may not depend on its host for the supply of this important molecule.
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Project description:Biological systems, ranging from bacteria and fungi to humans, can methylate arsenic. Recent studies have suggested that the AsIII S-adenosylmethionine methyltransferase (arsM) gene in bacteria was responsible for the removal of arsenic as the volatile arsines from the bacteria. However, there has been no direct measure of the arsines released from bacteria cultures. We describe here an integrated system incorporating the bacterial incubation and volatile arsenic species analysis, and we demonstrate its application to the identification of the volatile arsines produced in bacterial cultures. The headspace of the bacterial cultures was purged with helium, and the volatile arsenic species were trapped in a chromatographic column immersed in liquid nitrogen. The cryogenically trapped arsines [AsH3, (CH3)AsH2, (CH3)2AsH, and (CH3)3As] were separated by gas chromatography and were detected by inductively coupled plasma mass spectrometry. A hydride generation system was coupled to the bacterial culture system, allowing for spiking standards and for generating calibration arsines necessary for quantitative analysis. Both bacteria containing the arsM gene or its variant arsMC2 gene were able to produce 400-500 ng of trimethylarsine. No trimethylarsine was detectable in bacteria lacking the arsM gene (containing the vector plasmid as negative control). These results confirm that arsM is responsible for releasing arsenic as volatile species from the arsenic-resistant bacteria. Our results also show traces of AsH3, CH3AsH2, and (CH3)2AsH in cultures of bacteria expressing arsM. The method detection limits for AsH3, CH3AsH2, (CH3)2AsH, and (CH3)3As were 0.5, 0.5, 0.7, and 0.6 pg, respectively. The ability to quantify trace levels of these volatile arsenic species makes it possible to study the biotransformation and biochemical roles of the evolution of these volatile arsenic species by biological systems.
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Project description:The udhA gene of Escherichia coli was cloned and expressed in E. coli and found to encode an enzyme with soluble pyridine nucleotide transhydrogenase activity. The N-terminal end of the enzyme contains the fingerprint motif of a dinucleotide binding domain, not present in published E. coli genome sequences due to a sequencing error. E. coli is hereby the first organism reported to possess both a soluble and a membrane-bound pyridine nucleotide transhydrogenase.
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Project description:Naturally occurring tRNAs contain numerous modified nucleosides. They are formed by enzymatic modification of the primary transcripts during the complex RNA maturation process. In model organisms Escherichia coli and Saccharomyces cerevisiae most enzymes involved in this process have been identified. Interestingly, it was found that tRNA methylation, one of the most common modifications, can be introduced by S-adenosyl-L-methionine (AdoMet)-dependent methyltransferases (MTases) that belong to two structurally and phylogenetically unrelated protein superfamilies: RFM and SPOUT.As a part of a large-scale project aiming at characterization of a complete set of RNA modification enzymes of model organisms, we have studied the Escherichia coli proteins YibK, LasT, YfhQ, and YbeA for their ability to introduce the last unassigned methylations of ribose at positions 32 and 34 of the tRNA anticodon loop. We found that YfhQ catalyzes the AdoMet-dependent formation of Cm32 or Um32 in tRNASer1 and tRNAGln2 and that an E. coli strain with a disrupted yfhQ gene lacks the tRNA:Cm32/Um32 methyltransferase activity. Thus, we propose to rename YfhQ as TrMet(Xm32) according to the recently proposed, uniform nomenclature for all RNA modification enzymes, or TrmJ, according to the traditional nomenclature for bacterial tRNA MTases.Our results reveal that methylation at position 32 is carried out by completely unrelated TrMet(Xm32) enzymes in eukaryota and prokaryota (RFM superfamily member Trm7 and SPOUT superfamily member TrmJ, respectively), mirroring the scenario observed in the case of the m1G37 modification (introduced by the RFM member Trm5 in eukaryota and archaea, and by the SPOUT member TrmD in bacteria).
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Project description:1. The hemD gene, encoding uroporphyrinogen III synthase, has been located adjacent to the hemC gene at 85 min on the Escherichia coli chromosome. 2. The entire nucleotide sequence (741 base pairs) of the hemD gene is reported. 3. E. coli strains harbouring plasmics containing the hemD gene produce greatly elevated levels of uroporphyrinogen III synthase. 4. Purified uroporphyrinogen III synthase, isolated from the hemD-containing strain ST1046, has an Mr of 29,000, in close agreement with that predicted from the nucleotide sequence. 5. The existence of a hem operon is suggested.
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Project description:We isolated an Escherichia coli mutant strain that suppresses the glycolate-negative phenotype of a strain deficient in both GlcA and LldP transporters of this compound. This suppressing phenotype was assigned to yjcG, a gene whose function was previously unknown, which was found to encode a membrane protein able to transport glycolate. On the basis of sequence similarity, the yjcG gene product was classified as a member of the sodium:solute symporter family. Northern experiments revealed that yjcG is cotranscribed with its neighbor, acs, encoding acetyl coenzyme A synthetase, which is involved in the scavenging acetate. The fortuitous presence of an IS2 element in acs, which impaired yjcG expression by polarity in our parental strain, allowed us to conclude that the alternative glycolate carrier became active after precise excision of IS2 in the suppressed strain. The finding that yjcG encodes a putative membrane carrier for glycolate and the cotranscription of yjcG with acs suggested that the primary function of the yjcG gene product (proposed gene name, actP) could be acetate transport and allowed us to define an operon involved in acetate metabolism. The time course of [1,2-(14)C]acetate uptake and the results of a concentration kinetics analysis performed with cells expressing ActP or cells deficient in ActP supported the the hypothesis that this carrier is an acetate transporter and suggested that there may be another transport system for this monocarboxylate.
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