Characterization of the DNA binding domain of StbA, a key protein of a new type of DNA segregation system

Quebre, V.; del Campo, I.; Cuevas, A.; Siguier, P.; Rech, J.; Phan Thai Nguyen, L.; hoang, b.; Cornet, F.; bouet, j.-y.; Moncalian, G.; de la Cruz, F.; Guynet, C.

doi:10.1101/2022.04.29.490116

bioRxiv · 10.1101/2022.04.29.490116

Characterization of the DNA binding domain of StbA, a key protein of a new type of DNA segregation system

Quebre, V.·del Campo, I.·Cuevas, A.·Siguier, P.·Rech, J.·Phan Thai Nguyen, L.·hoang, b.·Cornet, F.·bouet, j.-y.·Moncalian, G.·de la Cruz, F.·Guynet, C.

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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 [A] resolution. It folds into an HTH DNA-binding motif, 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.

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Quebre, V., del Campo, I., Cuevas, A., Siguier, P., Rech, J., Phan Thai Nguyen, L., hoang, b., Cornet, F., bouet, j.-y., Moncalian, G., de la Cruz, F., Guynet, C.. 2022-04-30. Characterization of the DNA binding domain of StbA, a key protein of a new type of DNA segregation system. https://doi.org/10.1101/2022.04.29.490116

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