NOVEL PROTEINS OF THE PHOSPHOTRANSFERASE SYSTEM ENCODED WITHIN THE RPON OPERON OF ESCHERICHIA-COLI - ENZYME IIA(NTR) AFFECTS GROWTH ON ORGANIC NITROGEN AND THE CONDITIONAL LETHALITY OF AN ERA(TS) MUTANT
Bs. Powell et al., NOVEL PROTEINS OF THE PHOSPHOTRANSFERASE SYSTEM ENCODED WITHIN THE RPON OPERON OF ESCHERICHIA-COLI - ENZYME IIA(NTR) AFFECTS GROWTH ON ORGANIC NITROGEN AND THE CONDITIONAL LETHALITY OF AN ERA(TS) MUTANT, The Journal of biological chemistry, 270(9), 1995, pp. 4822-4839
Two rpoN-linked Delta Tn10-kan insertions suppress the conditionally l
ethal era(ts) allele. One truncates rpoN while the second disrupts ano
ther gene (ptsN) in the rpoN operon and does not affect classical nitr
ogen regulation. Neither alter expression of era indicating that suppr
ession is post-translational. Plasmid clones of ptsN prevent suppressi
on by either disruption mutation indicating that this gene is importan
t for lethality caused by era(ts). rpoN and six neighboring genes were
sequenced and compared with sequences in the database. Two of these g
enes encode proteins homologous to Enzyme IIA(Fru) and HPr of the phos
phoenolpyruvate:sugar phosphotransferase system. We designate these pr
oteins IIA(Ntr) (ptsN) and NPr (npr). Purified IIA(Ntr) and NPr exchan
ge phosphate appropriately with Enzyme I, HPr, and Enzyme IIA proteins
of the phosphoenolpyruvate: sugar phosphotransferase system. Several
sugars and tricarboxylic acid cycle intermediates inhibited growth of
the ptsN disruption mutant on medium containing an amino acid or nucle
oside base as a combined source of nitrogen, carbon, and energy. This
growth inhibition was relieved by supplying the ptsN gene or ammonium
salts but was not aleviated by altering levels of exogenously supplied
cAMP. These results support our previous proposal of a novel mechanis
m linking carbon and nitrogen assimilation and relates IIA(Ntr) to the
unknown process regulated by the essential GTPase Era.