The
RidA (YjgF/YER057c/UK114) family of
proteins is broadly conserved in the three domains of life yet the functional understanding of these
proteins is at an early stage. Physiological studies of
ridA mutant strains of Salmonella enterica provided a framework to inform in vitro studies and led to the description of a conserved biochemical activity for this family.
ridA mutant strains of S. enterica have characteristic phenotypes including new synthesis of
thiamine biosynthetic intermediate
phosphoribosylamine (PRA), inability to grow on
pyruvate as a sole
carbon and energy source or when
serine is present in the minimal growth medium, and a decreased specific activity of
transaminase B (IlvE). Secondary mutations restoring growth to a
ridA mutant in the presence of
serine were in dapA (encoding
dihydrodipicolinate synthase) and thrA (encoding
homoserine dehydrogenase). These mutations suppressed multiple
ridA mutant phenotypes by increasing the synthesis of
threonine. The ability of
threonine to suppress the metabolic defects of a
ridA mutant is discussed in the context of recent biochemical data and in vivo results presented here.