Characterization of the DNA Binding Domain of StbA, A Key Protein of A New Type of DNA Segregation System. Issue 19 (15th October 2022)

• Record Type: Journal Article
• Authors: Quèbre, Valentin; del Campo, Irene; Cuevas, Ana; Siguier, Patricia; Rech, Jérôme; Le, Phan Thai Nguyen; Ton-Hoang, Bao; Cornet, François; Bouet, Jean-Yves; Moncalian, Gabriel; de la Cruz, Fernando; Guynet, Catherine
• Is Part Of: Journal of molecular biology. Volume 434:Issue 19(2022)
• Publication Date: 2022-10-15
• Subjects: plasmid -- DNA segregation -- bacterial conjugation -- transcription factor -- helix-turn-helix; CBP Centromere Binding Protein -- PTU plasmid taxonomic units -- HTH Helix Turn Helix -- DR Direct Repeat; Molecular biology -- Periodicals; Biology -- Periodicals; Biochemistry -- Periodicals; Bacteriology -- Periodicals; Molecular Biology -- Periodicals; Biochemistry -- Periodicals; Biologie moléculaire -- Périodiques; Biologie -- Périodiques; Biochimie -- Périodiques; Moleculaire biologie; Biochemistry; Biology; Molecular biology; Periodicals; 572.805
• DOI: 10.1016/j.jmb.2022.167752
• Languages: English
• ISSNs: 0022-2836

Abstract

Graphical abstract: Highlights: The N-ter DNA binding domain of StbA is structurally related to the PadR regulators. The C-terminal domain of StbA is required for both segregation and conjugation. Plasmid R388 conjugation depends on its subcellular positioning. Abstract: Low-copy-number plasmids require sophisticated genetic devices to achieve efficient segregation of plasmid copies during cell division. Plasmid R388 uses a unique segregation mechanism, based on StbA, a small multifunctional protein. StbA is the key protein in a segregation system not involving a plasmid-encoded NTPase partner, it regulates the expression of several plasmid operons, and it is the main regulator of plasmid conjugation. The mechanisms by which StbA, together with the centromere-like sequence stbS, achieves segregation, is largely uncharacterized. To better understand the molecular basis of R388 segregation, we determined the crystal structure of the conserved N-terminal domain of StbA to 1.9 Å resolution. It folds into an HTH DNA-binding domain, structurally related to that of the PadR subfamily II of transcriptional regulators. StbA is organized in two domains. Its N-terminal domain carries the specific stbS DNA binding activity. A truncated version of StbA, deleted of its C-terminal domain, displays only partial activities in vivo, indicating that the non-conserved C-terminal domain is required for efficient segregation and subcellular plasmid positioning. The structure of StbA DNA-binding domain also provides some insight into how StbA monomers cooperate to repress transcription by binding to the stbDR and to form the segregation complex with stbS .