Over the next 40 minutes or so,
I'd like to describe
our current understanding
of how nucleotide-dependent
I would describe
how one major variant sigma factor,
an RNA polymerase subunit participates
in this process
of transcriptional activation.
I'll describe in detail its activators
and in particular
I will describe how nucleotide,
in particular ATP,
in the transcriptional activator.
And that will be based on
recent structural studies
on a transcriptional activator from E. coli,
the so-called phage shock protein F, PspF,
an E. coli transcriptional activator.
Bacteria use proteins called sigma factors
to bring RNA polymerase to the promoter DNA.
Typically, they exist in two classes,
the sigma70 class
which is well represented
with many members.
Here we see in E. coli
there are one, two, three, four, five,
six members of the sigma70 class.
The focus of my talk
is on an alternative sigma factor
called sigma54, it's got a single member.
Sometimes, it's only one of
only two sigma factors in bacteria,
and it really provides an example
of a transcriptional activation mechanism
that resembles eukaryotic enhancer-dependent
Here we see the organization in E. coli
of the RNA polymerase sigma relationship.
The sigma70 type factors
combine with the core RNA polymerase
to form a sigma70 type holoenzyme.
The sigma54 factor
combines with the same core enzyme
to form the sigma54
RNA polymerase holoenzyme.
The important point here
is that the sigma54
containing RNA polymerase
has got very, very different requirements
to initiate transcription
compared to the sigma70 RNA polymerase.
sigma54 RNA polymerase requires
the use of ATP hydrolysis
to drive the formation
of the DNA melting step in transcription.