FIG. 4.
Gel retardation of DNA fragments from the glnB and glnA promoter regions by cell extracts of an NtcA-overproducing E. coli strain. (A) glnA promoter region, PglnA (lanes 1 to 3), and glnB promoter region, PglnB (lanes 4 to 6), incubated with a DNA fragment internal to the glnB gene as the competitor DNA. Lanes 1 and 4, no NtcA-containing extract added; lanes 2 and 5, 5 μg of extract from cells of E. coli DH5α(pTrc99A) added; lanes 3 and 6, 5 μg of NtcA-containing extract from IPTG-induced cells of E. coli DH5α(pCSI26) added. CglnA and CglnB are complexes formed after incubation of the DNA fragments carrying PglnA and PglnB, respectively, with the NtcA-containing extracts. (B) Same conditions as in panel A, lanes 1 and 4, with various amounts (0 [−] to 8.0 μg) of extract from IPTG-induced cells of E. coli DH5α(pCSI26) added.