Inhibition of aminoacyl-transfer ribonucleic acid synthetases and the regulation of amino acid biosynthetic enzymes in Neurospora crassa.
(9/21)
Growth conditions that result in the accumulation of the tryptophan intermediate indoleglycerol phosphate or of the histidine intermediate imidazoleglycerol phosphate cause mycelia of Neurospora crassa to exhibit an immediate and sustained increase in the differential rate at which the biosynthetic enzymes of the tryptophan, histidine, and arginine pathways are synthesized. These accumulated intermediates are shown to be inhibitors of the activity of aminoacyltransfer ribonucleic acid (tRNA) synthetases, as judged by an in vitro esterification assay. The tryptophan intermediate is shown to inhibit the charging of tryptophan, and the histidine intermediate is shown to inhibit charging of histidine. The inhibitions noted are consistent with the finding that the level of charged tRNATrp is decreased significantly in cells that have accumulated indoleglycerol phosphate and that of tRNAHis is decreased significantly in cells that have accumulated imidazoleglycerol phosphate. These results are interpreted as support for the involvement of aminoacyl-tRNA species in mediating cross-pathway regulation of the tryptophan, histidine, and arginine biosynthetic pathways as proposed in Lester's polyrepressor hypothesis (G. Lester, 1971). the correlations noted lead to the conclusion that Neurospora utilizes regulatory mechanisms that have the ability to react to changes in the level of charging of tRNA species. (+info)
Characterization of DNA polymerase X from Thermus thermophilus HB8 reveals the POLXc and PHP domains are both required for 3'-5' exonuclease activity.
(10/21)
Biochemical characterization of an Escherichia coli hisT strain.
(11/21)
An Escherichia coli hisT strain was characterized biochemically and shown to contain altered transfer ribonucleic acid and to be altered in the regulation of amino acid biosynthesis. (+info)
Crystallization and preliminary X-ray crystallographic analysis of a novel histidinol-phosphate phosphatase from Thermococcus onnurineus NA1.
(12/21)
The missing link in plant histidine biosynthesis: Arabidopsis myoinositol monophosphatase-like2 encodes a functional histidinol-phosphate phosphatase.
(13/21)
Expression of the histidine operon in rho mutants of Escherichia coli.
(16/21)
Expression of the Escherichia coli histidine operon was measured in four independently isolated sets of strains carrying ten different rho mutations. Rho factor does not act as a major regulatory element of histidine operon attenuation. (+info)