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Phosphoglucose isomerase (PGI) was purified from Aspergillus niger and the in vitro kinetic properties of the enzyme were related to its functioning in vivo. A new assay method was developed to study the forward reaction making use of mannitol 1-P dehydrogenase as the coupling enzyme. In this simple assay system mannitol 1-P dehydrogenase converts fructose 6-P and NADH to mannitol 1-P and NAD ...
Exogenous inorganic pyrophosphate increases the biomass yield of Escherichia coli. In this report, we show that the effect of pyrophosphate is related to iron uptake. We have found that addition of pyrophosphate, ammonium iron (III) citrate or iron (III) chloride, in M63 minimal medium containing 1.7 μM of iron, causes an increase in growth yield. In contrast to iron chloride or ammonium iron (III)...
p 1 , p 4 -Diadenosine 5'-tetraphosphate (Ap 4 A) has been implicated as a modulator of blood vessel tone. We have recently demonstrated that the infusion of Ap 4 A into swine induces vasodilation (Hilderman et al., Am. J. Hypertension 10 (1997) 94A) and that Ap 4 A induces the release of nitric oxide (NO) from bovine aortic endothelial cells (BAEC) (Hilderman...
The regulation of transcription of the pckA gene coding for phosphoenolpyruvate carboxykinase in Escherichia coli was analysed by site-directed mutagenesis of the promoter region and measurement of in vitro transcription initiation. Mutation of the guanine residue at position –14 to either cytosine or thymine was found to result in a drastic decrease of transcription, even in the presence of the natural...
A minor low-sulphated dermatan sulphate proteoglycan was isolated from ray skin by extraction with 2% sodium dodecyl sulphate, followed with ion-exchange chromatography, gel chromatography and density gradient centrifugation. The proteoglycan with a relative molecular mass (M r ) ranging from 70 to 120 kDa is composed of about two dermatan sulphate chains (M r 33 kDa) bound on a protein...
The C-terminal domain (residues 320–419) of tyrosyl-tRNA synthetase (TyrRS) from Bacillus stearothermophilus is disordered in the crystal structure and involved in the binding of the anticodon arm of tRNA Tyr . The sequences of 11 TyrRSs of prokaryotic or mitochondrial origins were aligned and the alignment showed the existence of conserved residues in the sequences of the C-terminal domains...
Sequence analysis of the far-upstream region of the human HLA-DRA gene has revealed the presence of Y' and X' boxes, highly homologous to the well characterized Y and X boxes present within the proximal-promoter region. Comparison of Y, Y', X, and X' box sequences present within different class II MHC genes of different species demonstrates that these boxes are conserved during evolution, suggesting...
In mammals, most of the selenium contained in their body is present as an unusual amino acid, selenocysteine (Sec), whose codon is UGA. Because the UGA codon is normally recognized as a translational stop signal, it is intriguing how cells recognize and distinguish the UGA Sec codon from the UGA stop codon. In eukaryotic selenoprotein mRNAs, it has been proposed that a conserved stem-loop structure...
The restriction endonuclease BstVI from Bacillus stearothermophilus V contains three cysteine residues at positions 134, 167 and 180. Titration of Cys residues with DTNB showed that none of them are involved in disulphide bond formation. Cysteine triplets 134 and 167 were modified by recombinant PCR to introduce a serine residue in each case. The mutated genes were cloned into pGEM-T vector and transformed...
The synthesis of diadenosine hexaphosphate (Ap 6 A), a potent vasoconstrictor, is catalyzed by acyl-CoA synthetase from Pseudomonas fragi. In a first step AMP is transferred from ATP to tetrapolyphosphate (P 4 ) originating adenosine pentaphosphate (p 5 A) which, subsequently, is the acceptor of another AMP moiety from ATP generating diadenosine hexaphosphate (Ap 6 ...
The conformation in solution of a small bipartite I-III hammerhead ribozyme has been deduced from the photo-cross-links formed between cleavable ribo-deoxysubstrates appropriately substituted with the probe deoxy-4-thiouridine and ribozyme residues. The ribozyme-substrate complex is able to adopt a Y-like structure with stems I and II in close proximity in the presence of 400 mM Na + only...
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