Structural highlights
Function
[COPG_STRAG] Regulates the plasmid copy number. Binds to the RepAB promoter thus controlling the synthesis of the plasmid replication initiator protein RepB.[1] [2]
Publication Abstract from PubMed
The structure of the 45 amino acid transcriptional repressor, CopG, has been solved unliganded and bound to its target operator DNA. The protein, encoded by the promiscuous streptococcal plasmid pMV158, is involved in the control of plasmid copy number. The structure of this protein repressor, which is the shortest reported to date and the first isolated from a plasmid, has a homodimeric ribbon-helix-helix arrangement. It is the prototype for a family of homologous plasmid repressors. CopG cooperatively associates, completely protecting several turns on one face of the double helix in both directions from a 13-bp pseudosymmetric primary DNA recognition element. In the complex structure, one protein tetramer binds at one face of a 19-bp oligonucleotide, containing the pseudosymmetric element, with two beta-ribbons inserted into the major groove. The DNA is bent 60 degrees by compression of both major and minor grooves. The protein dimer displays topological similarity to Arc and MetJ repressors. Nevertheless, the functional tetramer has a unique structure with the two vicinal recognition ribbon elements at a short distance, thus inducing strong DNA bend. Further structural resemblance is found with helix-turn-helix regions of unrelated DNA-binding proteins. In contrast to these, however, the bihelical region of CopG has a role in oligomerization instead of DNA recognition. This observation unveils an evolutionary link between ribbon-helix-helix and helix-turn-helix proteins.
The structure of plasmid-encoded transcriptional repressor CopG unliganded and bound to its operator.,Gomis-Ruth FX, Sola M, Acebo P, Parraga A, Guasch A, Eritja R, Gonzalez A, Espinosa M, del Solar G, Coll M EMBO J. 1998 Dec 15;17(24):7404-15. PMID:9857196[3]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ del Solar GH, de al Campa AG, Perez-Martin J, Choli T, Espinosa M. Purification and characterization of RepA, a protein involved in the copy number control of plasmid pLS1. Nucleic Acids Res. 1989 Apr 11;17(7):2405-20. PMID:2497439
- ↑ del Solar GH, Perez-Martin J, Espinosa M. Plasmid pLS1-encoded RepA protein regulates transcription from repAB promoter by binding to a DNA sequence containing a 13-base pair symmetric element. J Biol Chem. 1990 Jul 25;265(21):12569-75. PMID:2373704
- ↑ Gomis-Ruth FX, Sola M, Acebo P, Parraga A, Guasch A, Eritja R, Gonzalez A, Espinosa M, del Solar G, Coll M. The structure of plasmid-encoded transcriptional repressor CopG unliganded and bound to its operator. EMBO J. 1998 Dec 15;17(24):7404-15. PMID:9857196 doi:10.1093/emboj/17.24.7404
