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Category: Bacterial Pathogenesis
Aromatic Amino Acid Metabolism in Bacillus subtilis, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555817992/9781555812058_Chap17-1.gif /docserver/preview/fulltext/10.1128/9781555817992/9781555812058_Chap17-2.gifAbstract:
Most proteins of Bacillus subtilis contain the three aromatic amino acids--phenylalanine, tyrosine, and tryptophan--all of which are synthesized from a common precursor, chorismate. The known and putative B. subtilis genes of aromatic amino acid metabolism, their location and presumed organization in operons, and their likely enzyme products or function are summarized in this chapter. Important distinctions between B. subtilis and Escherichia coli with regard to aromatic amino acid metabolism are the existence of a multifunctional aromatic supraoperon in B. subtilis and this organism's use of cross-pathway regulation of gene expression. Trp RNA-binding attenuation protein (TRAP) activation is reduced when the hydrogen bond between Tht52 and the catboxyl group of tryptophan is prevented. The affinity of TRAP for tryptophan increases in the presence of bound RNA. In B. subtilis, the biosynthetic pathways for folate and tryptophan are highly interconnected. First, both pathways use chorismate and glutamine to synthesize the p-aminobenzoic acid and o-aminobenzoic acid precursors of folate and tryptophan, respectively. Next, the TrpG polypeptide functions as the glutamine amidotransferase component of two enzyme complexes. Further, the mtrAB operon encodes TRAP (mtrB) and GTP cyclohydrolase I (mrrA). Finally, TRAP negatively regulates both biosynthetic pathways in response to tryptophan. The chapter talks about tRNA trp regulation of trp gene expression, a gene coding for a putative tryptophan transport protein, and homologous polypeptides in some other bacterial species.
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Enzymes, genes, and reactions of the common aromatic pathway leading to the synthesis of chorismate, the precursor of phenylalanine, tyrosine, tryptophan, and several other aromatic compounds.
Enzymes, genes, and reactions of the common aromatic pathway leading to the synthesis of chorismate, the precursor of phenylalanine, tyrosine, tryptophan, and several other aromatic compounds.
Enzymes, genes, and reactions of the pathways leading to the synthesis of phenylalanine and tyrosine from chorismate.
Enzymes, genes, and reactions of the pathways leading to the synthesis of phenylalanine and tyrosine from chorismate.
Enzymes, genes, and reactions of the pathway leading to the synthesis of tryptophan from chorismate.
Enzymes, genes, and reactions of the pathway leading to the synthesis of tryptophan from chorismate.
Transcription attenuation model for the trpEDCFBA operon.
Transcription attenuation model for the trpEDCFBA operon.
Translational control model for trpE.
Translational control model for trpE.
Operon organization of the genes of aromatic amino acid metabolism a
a Genes for tRNAs and tRNA synthecases are not shown.
b Map position reflects the relative gene position on the chromosome map.
c Transcription orientation. F, forward, clockwise; R, reverse, counterclockwise.
d Intergenic spacing (negative number indicates genes overlap); or number of nucleotides from the promoter to the first gene of the operon.
e Alternative name: para-aminobenzoate synthase glutamine amidotransferase subunit B.
f Transcription also starts from the trpE promoter localized 203 bp upstream from its ATG start codon.
g Alternative name: L-serine hydrolyase.
h Alternative name: indole-3-glycerol phosphate aldolase.
i Alternative name: hisC.
j Alternative name: 3-phosphoshikimate 1-carboxyvinyltransferase.
k Alternative name: aroG. Bifunctional enzyme. DAHP syntase/chorismate mutase.
l Alternative name: phospho-2-dehydro-3'deoxyheptonate aldolase.
Operon organization of the genes of aromatic amino acid metabolism a
a Genes for tRNAs and tRNA synthecases are not shown.
b Map position reflects the relative gene position on the chromosome map.
c Transcription orientation. F, forward, clockwise; R, reverse, counterclockwise.
d Intergenic spacing (negative number indicates genes overlap); or number of nucleotides from the promoter to the first gene of the operon.
e Alternative name: para-aminobenzoate synthase glutamine amidotransferase subunit B.
f Transcription also starts from the trpE promoter localized 203 bp upstream from its ATG start codon.
g Alternative name: L-serine hydrolyase.
h Alternative name: indole-3-glycerol phosphate aldolase.
i Alternative name: hisC.
j Alternative name: 3-phosphoshikimate 1-carboxyvinyltransferase.
k Alternative name: aroG. Bifunctional enzyme. DAHP syntase/chorismate mutase.
l Alternative name: phospho-2-dehydro-3'deoxyheptonate aldolase.
Polypeptide homologs in some other species (percent identity of the amino acid sequence with the B. subtilis sequence) a
a The fully sequenced genomes analyzed were B. subtilis (AL009126), E. coli (U00096), Deinococcus radiodurcms chromosomes 1 (AE000513) and 2 (AE001825), Methanobacterium thermoautotrophicum (AE000666), Mycoplasma genitalium (L43967), Mycoplasma pneumoniae (U00089), and Mycobacterium tuberculosis (AL123456). Partially sequenced genomes are from NCBI-GenBank Flat File Release 109.0. Owing to the multidomain nature of some enzymes in the pathways, comparisons were restricted to common functional domains using the local alignment program ssearch3, designed for full-length protein comparisons ( 32 ). No homologs of B. subtilis YhaG, YczA, and YcbK were found; therefore, the corresponding proteins were omitted from this table.
b Bifunctional enzyme: DAHP syntase/chorismate mutase.
c N.s., there is biochemical evidence of this activity, but the search did not find a statistically significant similarity.
d There are three different versions of this enzyme.
e N.f., not found.
f Bifunctional enzyme: chorismate mutase/prephenate dehydratase.
g Bifunctional enzyme: chorismate mutase/prephenate dehydrogenase.
h This pathway also includes chorismate mutase and tyrosine/phenylalanine aminotransferase.
i Bifunctional enzyme: phosphoribosyl anthranilate isomerase/indole-3'glycerol phosphate synthase.
j Bifunctional enzyme: anthranilate synthase component II/anthranilate phosphoribosyltransferase.
k Bifunctional enzyme: phosphoribosyl anthranilate isomerase/indole-3-glycerol phosphate synthase.
l mtrB has also been sequenced from Bacillus pumilus ( 25 ).
Polypeptide homologs in some other species (percent identity of the amino acid sequence with the B. subtilis sequence) a
a The fully sequenced genomes analyzed were B. subtilis (AL009126), E. coli (U00096), Deinococcus radiodurcms chromosomes 1 (AE000513) and 2 (AE001825), Methanobacterium thermoautotrophicum (AE000666), Mycoplasma genitalium (L43967), Mycoplasma pneumoniae (U00089), and Mycobacterium tuberculosis (AL123456). Partially sequenced genomes are from NCBI-GenBank Flat File Release 109.0. Owing to the multidomain nature of some enzymes in the pathways, comparisons were restricted to common functional domains using the local alignment program ssearch3, designed for full-length protein comparisons ( 32 ). No homologs of B. subtilis YhaG, YczA, and YcbK were found; therefore, the corresponding proteins were omitted from this table.
b Bifunctional enzyme: DAHP syntase/chorismate mutase.
c N.s., there is biochemical evidence of this activity, but the search did not find a statistically significant similarity.
d There are three different versions of this enzyme.
e N.f., not found.
f Bifunctional enzyme: chorismate mutase/prephenate dehydratase.
g Bifunctional enzyme: chorismate mutase/prephenate dehydrogenase.
h This pathway also includes chorismate mutase and tyrosine/phenylalanine aminotransferase.
i Bifunctional enzyme: phosphoribosyl anthranilate isomerase/indole-3'glycerol phosphate synthase.
j Bifunctional enzyme: anthranilate synthase component II/anthranilate phosphoribosyltransferase.
k Bifunctional enzyme: phosphoribosyl anthranilate isomerase/indole-3-glycerol phosphate synthase.
l mtrB has also been sequenced from Bacillus pumilus ( 25 ).