Molecular and General Genetics MGG

, Volume 219, Issue 1, pp 26–32

The F plasmid ccd autorepressor is a complex of CcdA and CcdB proteins

  • Jeffrey E. Tam
  • Bruce C. Kline

DOI: 10.1007/BF00261153

Cite this article as:
Tam, J.E. & Kline, B.C. Molec. Gen. Genet. (1989) 219: 26. doi:10.1007/BF00261153


The ccd operon of plasmid F produces three proteins, CcdA, CcdB, and RepD. Prior research has established that the operon is autorepressed and that at least CcdB, but not RepD, is required for autorepression. A role for CcdA in autorepression was suggested but not clearly shown. We now present a series of biochemical experiments which show that both CcdA and CcdB proteins are required for maximal formation of protein-ccd operator complexes. We also show that CcdA and CcdB are present in a complex whether or not ccd operator is present. The clear implication is that autorepressor is a complex of CcdA and CcdB. We also map the start site of the ccd transcript thus providing the first experimental evidence for the location of the ccd promoter.

Key words

F plasmid ccd Autorepressor 

Copyright information

© Springer-Verlag 1989

Authors and Affiliations

  • Jeffrey E. Tam
    • 1
  • Bruce C. Kline
    • 1
  1. 1.Department of Biochemistry and Molecular BiologyMayo Clinic/FoundationRochesterUSA
  2. 2.Department of Microbiology and ImmunologyUniversity of North CarolinaChapel HillUSA