Nucleoprotein structures at positively regulated bacterial promoters: homology with replication origins and some hypotheses on the quaternary structure of the activator proteins in these complexes.

The quaternary structure of regulatory proteins undoubtedly plays an important role in the initiation of transcription and DNA replication. To date, the best-characterized regulatory proteins are oligomers in which promoters are bound together by isologous interactions. From the examples presented in this article, it appears that the formation of certain nucleoprotein complexes implicated in transcription initiation might involve heterologous rather than isologous interactions, allowing differentiation between two classes of transcription activators. Nucleoprotein structures present at the oriC replication origin and at malB promoters show striking homologies.