DNA-BINDING ACTIVITY OF NTRC FROM RHIZOBIUM GROWN ON DIFFERENT NITROGEN-SOURCES

The DNA-binding activity of the NtrC protein can be demonstrated in ge l retardation assays with concentrated protein extracts of Rhizobium e tli. Using extracts from either the wild type or a ntrC mutant strain and an antiserum raised against the NtrC protein, we demonstrate speci fic binding of NtrC to the upstream regulatory region of the glnII gen e, where two putative NtrC-binding sites are present. KNO3-grown bacte ria contain less NtrC protein and more NtrC-binding activity than NH4C l-grown bacteria, thus showing that with this protocol it is possible to detect changes in NtrC-binding activity. The advantages of this ass ay system in comparison with that using pure proteins is discussed.