ABSTRACTEscherichia coliYggS (COG0325) is a member of the highly conserved pyridoxal 5′-phosphate (PLP)-binding protein (PLPBP) family. Recent studies suggested a role for this protein family in the homeostasis of vitamin B6and amino acids. The deletion or mutation of a member of this protein family causes pleiotropic effects in many organisms and is causative of vitamin B6-dependent epilepsy in humans. To date, little has been known about the mechanism by which lack of YggS results in these diverse phenotypes. In this study, we determined that the pyridoxine (PN) sensitivity observed inyggS-deficientE. coliwas caused by the pyridoxine 5′-phosphate (PNP)-dependent overproduction of Val, which is toxic toE. coli. The data suggest that theyggSmutation impacts Val accumulation by perturbing the biosynthetic of Thr from homoserine (Hse). Exogenous Hse inhibited the growth of theyggSmutant, caused further accumulation of PNP, and increased the levels of some intermediates in the Thr-Ile-Val metabolic pathways. Blocking the Thr biosynthetic pathway or decreasing the intracellular PNP levels abolished the perturbations of amino acid metabolism caused by the exogenous PN and Hse. Our data showed that a high concentration of intracellular PNP is the root cause of at least some of the pleiotropic phenotypes described for ayggSmutant ofE. coli.IMPORTANCERecent studies showed that deletion or mutation of members of the YggS protein family causes pleiotropic effects in many organisms. Little is known about the causes, mechanisms, and consequences of these diverse phenotypes. It was previously shown thatyggSmutations inE. coliresult in the accumulation of PNP and some metabolites in the Ile/Val biosynthetic pathway. This work revealed that some exogenous stresses increase the aberrant accumulation of PNP in theyggSmutant. In addition, the current report provides evidence indicating that some, but not all, of the phenotypes of theyggSmutant inE. coliare due to the elevated PNP level. These results will contribute to continuing efforts to determine the molecular functions of the members of the YggS protein family.
Vitamin B and Vitamin C Affect DNA Methylation and Amino Acid Metabolism in Mycobacterium bovis BCG
