Jay D. Gralla is in the Department of Chemistry Biochemistry,
University of California, Los Angeles, Los Angeles,
California 90095-1569, USA. gralla@chem.ucla.edu
Some prokaryotic transcriptional activators act by binding to enhancers
and directly changing the conformation of a specialized sigma factor in the
RNA polymerase holoenzyme. This mechanism has interesting parallels in other
transcription systems.
