Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A negative regulator gene for synthesis of arylsulfatase in Klebsiella aerogenes was cloned. Deletion analysis showed that the regulator gene was located within a 1.6-kb cloned segment. Transfer of the plasmid, which contains the cloned fragment, into constitutive atsR mutant strains of K. aerogenes resulted in complementation of atsR; the synthesis of arylsulfatase was repressed in the presence of inorganic sulfate or cysteine, and this repression was relieved, in each case, by the addition of tyramine. The nucleotide sequence of the 1.6-kb fragment was determined. From the amino acid sequence deduced from the DNA sequence, we found two open reading frames. One of them lacked the N-terminal region but was highly homologous to the gene which codes for diadenosine tetraphosphatase (apaH) in Escherichia coli. The other open reading frame was located counterclockwise to the apaH-like gene. This gene was highly homologous to the gene which codes for dihydrofolate reductase (folA) in E. coli. We detected 30 times more activity of dihydrofolate reductase in the K. aerogenes strains carrying the plasmid, which contains the arylsulfatase regulator gene, than in the strains without plasmid. Further deletion analysis showed that the K. aerogenes folA gene is consistent with the essential region required for the repression of arylsulfatase synthesis. Transfer of a plasmid containing the E. coli folA gene into atsR mutant cells of K. aerogenes resulted in repression of the arylsulfatase synthesis. Thus, we conclude that the folA gene codes a negative regulator for the ats operon.
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PMID:Cloning and nucleotide sequence of a negative regulator gene for Klebsiella aerogenes arylsulfatase synthesis and identification of the gene as folA. 155 51

The DNA sequences of the diadenosine tetraphosphatase gene (apaH) and of the flanking regions were determined. Three other genes were identified in the flanking regions: ksgA, apaG and folA encoding, respectively, a 16 S rRNA methyltransferase, an unidentified protein of Mr 13,826 and dihydrofolate reductase, with the order folA-apaH-apaG-ksgA. The apaH gene is thus located between folA and ksgA at 1 min on the Escherichia coli chromosome linkage map and folA is transcribed clockwise, whereas ksgA, apaG and apaH are transcribed in the opposite direction. It was shown that ksgA, apaG and apaH can be expressed from a polycistronic mRNA originating from a promoter (p1) located upstream of ksgA. However, another promoter (p2) was found within the ksgA structural gene. This promoter, active in vivo, can account for p1-independent expression of the two distal cistrons, apaG and apaH. Finally, the effect on diadenosine tetraphosphatase over-production of a frameshift mutation causing premature translational termination of apaG suggests that expression of apaG and apaH is coupled at the translational level.
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PMID:The gene for Escherichia coli diadenosine tetraphosphatase is located immediately clockwise to folA and forms an operon with ksgA. 303 29

'Halophilic adaptation' of proteins, i.e. the requirement for high concentrations of monovalent ions for thermodynamic stability of proteins from halophilic organisms, is not fully understood. In this work, an explanation for the halophilic behavior of dihydrofolate reductase (h-DHFR) from Halobacterium volcanii is attempted, based on a model structure derived from comparative modeling to dihydrofolate reductase from Escherichia coli. The model structure of h-DHFR shows an unique asymmetrical charge distribution over the protein surface, with positively charged amino acids centered around the active site and negative charges on the opposite side of the enzyme. This particular charge distribution and the correlated molecular dipole are functionally relevant. The negative charges on the surface form clusters which are shielded at high salt concentrations; at low salt, they repulse each other, thus destabilizing the protein. Results are in accordance with denaturation data and, thus, provide an explanation for the exceptional stability properties of h-DHFR.
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PMID:A structure-based model for the halophilic adaptation of dihydrofolate reductase from Halobacterium volcanii. 817 Sep 25