Capacitance-derived dielectric constants demonstrate differential preinitiation complexes in TBP-independent and TBP-dependent transcription

The electronic properties of proteins and DNA may change dramatically upon complex formation, yet there are not many experimental methods which can be used to measure these properties. It has been previously shown that measuring the capacitance of a solution containing interacting DNA and protein species can yield information about changing dipole moments. The measured dielectric constant relates directly to the dipole moment of the complexes in solution. Here, we apply this method to partial transcription initiation complexes in order to investigate the changing electronic properties in the transcriptional preinitiation complex. These experiments are the first reported observations relating to the overall dipole moment and its changes in preinitiation complex formation. Comparing results from TBP-independent and TBP-dependent transcriptional systems shows a divergence in the electronic properties of built-up transcription complexes, suggesting that they initiate transcription by significantly different electronic and structural pathways. (C) 2004 Elsevier B.V. All rights reserved.