Fig 4.
EMSA of the binding of Anabaena NtcA to DNA sequences between the two TSPs of the devB gene. The DNA fragment of the devB promoter region represented in panel A (fragment a) was incubated, as indicated, with purified NtcA (plus 0.6 mM 2-OG, except when indicated in panel C) before loading onto PAGE gels. NtcA concentrations in panel B are as follows: 0.1, 0.5, 1.0, 1.5, 2.0, 2.5 3.0, 4.0, and 10.0 μM. NtcA concentrations in panel D are 0.6 μM. −, no NtcA added. Arrows in panel C point to the positions of NtcA-DNA complexes. (D) 100× or 200× excess of unlabeled DNA fragment (a and b are as represented in panel A) or 100×, 200×, or 300× excess of a fragment of the promoter of the Amaranthus hybridus psbA gene (PpsbA), added as indicated. Numbers under the pictures in panel D indicate percentages of retarded fragments in the corresponding lane (see Materials and Methods for details).