Xy. Liu et P. Matsumura, THE FLHD FLHC COMPLEX, A TRANSCRIPTIONAL ACTIVATOR OF THE ESCHERICHIA-COLI FLAGELLAR CLASS-II OPERONS, Journal of bacteriology, 176(23), 1994, pp. 7345-7351
The Escherichia coli flhD operon encodes two genes, flhD and flhC. Bot
h gene products were overproduced and purified. The purified proteins
formed a complex consisting of two FlhD and two FlhC molecules. Mobili
ty shift assays showed that the FlhD/FlhC complex had a DNA-binding ac
tivity and bound to the upstream regions of fliA, flhB, and fliL opero
ns (class II), which are under direct control of the flhD operon. DNas
e I footprinting analyses of FlhD/FlhC binding to the three class II p
romoter regions revealed protection of a 48-bp region of the fliA oper
on between positions -41 to -88, a 50-bp region of the flhB operon bet
ween positions -28 to -77, and a 48-bp region of the fliL operon betwe
en positions -29 to -76. In vitro transcription experiments demonstrat
ed that the FlhD/FlhC complex is a transcriptional activator required
for the transcription of the three class II operons examined in vitro.