The replication initiator of the cholera pathogen’s second chromosome shows structural similarity to plasmid initiators

Authors

Natalia Orlova, CUNY Graduate CenterFollow
Matthew Gerding, Harvard University
Olha Ivashkiv, CUNY City College
Paul Dominic B. Olinares, Rockefeller University
Brian T. Chait, Rockefeller University
Matthew K. Waldor, Harvard University
David Jeruzalmi, CUNY City CollegeFollow

Document Type

Article

Publication Date

12-28-2016

Abstract

The conserved DnaA-oriC system is used to initiate replication of primary chromosomes throughout the bacterial kingdom; however, bacteria with multipartite genomes evolved distinct systems to initiate replication of secondary chromosomes. In the cholera pathogen, Vibrio cholerae, and in related species, secondary chromosome replication requires the RctB initiator protein. Here, we show that RctB consists of four domains. The structure of its central two domains resembles that of several plasmid replication initiators. RctB contains at least three DNA binding winged-helix-turn-helix motifs, and mutations within any of these severely compromise biological activity. In the structure, RctB adopts a headto- head dimeric configuration that likely reflects the arrangement in solution. Therefore, major structural reorganization likely accompanies complex formation on the head-to-tail array of binding sites in oriCII. Our findings support the hypothesis that the second Vibrionaceae chromosome arose from an ancestral plasmid, and that RctB may have evolved additional regulatory features.

Comments

This article was originally published in Nucleic Acids Research, available at doi: 10.1093/nar/gkw1288.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License.