Regulation of histidinol phosphate aminotransferase synthesis by tryptophan in Bacillus subtilis

Abstract

The effect of tryptophan on the synthesis of histidinol phosphate aminotransferase and prephenate dehydrogenase has been examined. The genes specifying two enzymes for tryptophan biosynthesis (anthranilate synthase and tryptophan synthase-B) were found to be derepressed in a temporal sequence according to their chromosomal location. The genes for histidinol phosphate aminotransferase and prephenate dehydrogenase were derepressed simultaneously approximately 8 min after tryptophan synthase-B. When excess tryptophan was added to a derepressed culture, the pattern of repression of trpE (anthranilate synthase), trpB (tryptophan synthase-B), hisH (histidinol phosphate aminotransferase), and tyrA (prephenate dehydrogenase) was found to be simultaneous. Methyl tryptophan-resistant mutants, which synthesize elevated levels of the tryptophan enzymes, also synthesized elevated levels of histidinol phosphate aminotransferase. Qualitatively similar data were obtained in a temperaturesensitive tryptophanyl-transfer ribonucleic acid synthetase mutant grown at elevated temperatures. The time at which messenger ribonucleic acid was synthesized for anthranilate synthase, tryptophan synthase-B, histidinol phosphate aminotransferase, and prephenate dehydrogenase in the presence of actinomycin D indicated that ordered enzyme synthesis was a result of ordered transcription of the corresponding portion of the genome. The effect of the drug rifampin on enzyme synthesis was also examined. The addition of this drug halted the transcription of anthranilate synthase very rapidly, but later regions of the tryptophan region continued to be transcribed. The transcription of the hisH and tyrA genes was also shut off rapidly after rifampin was added. The significance of these observations to the control of transcription of the hisH gene by tryptophan is discussed.

The glucose and nitrogen starvation response of Bacillus licheniformis

“…Beside the induction of these genes, also tyrA, encoding the prephenate dehydrogenase, was induced. In B. subtilis, a co-regulation of the trp genes with hisC and tyrA has been reported [64]. Expression of the genes involved in tryptophan biosynthesis is regulated in B. subtilis in response to the tryptophan availability by the trp RNA-binding attenuation protein (TRAP) [65].…”

Insights into the structural basis of substrate recognition by histidinol-phosphate aminotransferase fromCorynebacterium glutamicum

“…In these experiments the biosynthetic reaction was measured, with the exception of His-P because the substrate 3-(imidazol-4-yl)-2-oxopropyl phosphate was not accessible (Table 2). HisC is the only aminotransferase active in l-His formation in C. glutamicum since a hisC-deletion mutant of C. glutamicum requires l-His for growth (data not shown), similar to other bacteria such as E. coli or Bacillus subtilis (Garrick-Silversmith & Hartman, 1970;Weigent & Nester, 1976). The activity with phenylpyruvate (O-Phe) and the other aromatic oxoacids does not contribute to aromatic amino-acid synthesis in C. glutamicum in vivo (Marienhagen et al, 2005), possibly owing to the low affinity of HisC (see below).…”

“…3). In the amino-acid sequences of Z. mobilis and B. subtilis HisC a phenylalanine residue is located at this position and Sivaraman et al 2001 contribute to the observed broader substrate specificity for aromatic amino acids in these two enzymes (Gu et al, 1995;Weigent & Nester, 1976). Amino-acid replacement by sitedirected mutagenesis at this position (Tyr123Phe) led to only moderate changes in kinetic constants with the natural substrate and the reactions with aromatic substrates were influenced even less (Table 3).…”