Open AccessPhosphoribosyl diphosphate synthetase-independent NAD de novo synthesis in Escherichia coli: a new phenotype of phosphate regulon mutants
Author(s) -
Bjarne HoveJensen
Publication year - 1996
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.178.3.714-722.1996
Subject(s) - regulon , nad+ kinase , biology , derepression , quinolinate , biochemistry , phosphoribosyltransferase , mutant , escherichia coli , operon , microbiology and biotechnology , enzyme , gene , tryptophan , hypoxanthine guanine phosphoribosyltransferase , amino acid , psychological repression , gene expression , quinolinic acid
Phosphoribosyl diphosphate-lacking (delta prs) mutant strains of Escherichia coli require NAD, guanosine, uridine, histidine, and tryptophan for growth. NAD is required by phosphoribosyl diphosphate-lacking mutants because of lack of one of the substrates for the quinolinate phosphoribosyltransferase reaction, an enzyme of the NAD de novo pathway. Several NAD-independent mutants of a host from which prs had been deleted were isolated; all of them were shown to have lesions in the pstSCAB-phoU operon, in which mutations lead to derepression of the Pho regulon. In addition NAD-independent growth was dependent on a functional quinolinate phosphoribosyltransferase. The prs suppressor mutations led to the synthesis of a new phosphoryl compound that may act as a precursor for a new NAD biosynthetic pathway. This compound may be synthesized by the product of an unknown phosphate starvation-inducible gene of the Pho regulon because the ability of pst or phoU mutations to suppress the NAD requirement requires PhoB, the transcriptional activator of the Pho regulon.