The bacterial segrosome: a dynamic nucleoprotein machine for DNA trafficking and segregation

• Published in: Nature reviews. Microbiology 2006-02, Vol.4 (2), p.133-143
• Main Authors: Hayes, Finbarr, Barillà, Daniela
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Antibiotic resistance; Bacteria; Bacteria - genetics; Bacteria - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacterial Proteins - physiology; Biomedical and Life Sciences; Cell cycle; Cell division; Chromosomes; Deoxyribonucleic acid; DNA; Genes; Genetic engineering; Genome, Bacterial; Genomes; Infectious Diseases; Life Sciences; Medical Microbiology; Microbiology; Molecular Sequence Data; Nucleoproteins - genetics; Nucleoproteins - metabolism; Nucleoproteins - physiology; Parasitology; Plasmids; Proteins; review-article; Sequence Alignment; Virology
• ISSN: 1740-1526; 1740-1534
• DOI: 10.1038/nrmicro1342

Recently solved tertiary structures of partition proteins provide important insights into segrosome organization and assembly. Hayes and Barillà review recent advances in our understanding of the bacterial segrosome and plasmid partitioning, including the organization of partition modules, segrosome assembly and plasmid trafficking. Key Points Genome segregation is a fundamental process that all cells must perform with high accuracy and in precise coordination with other cell-cycle events. The molecular mechanisms that underpin plasmid and chromosome segregation in prokaryotes are the subject of intense investigation. The segrosome is the nucleoprotein molecular machine that directs the intracellular movement of plasmids during segregation. Plasmid segregation requires a pair of proteins that interacts with a centromere analogue. One protein is most commonly a member of the ParA superfamily of Walker-type ATPases, whereas the partner protein is a DNA-binding factor that interacts site-specifically with the plasmid centromere analogue. Plasmid centromeres have diverse organizations, although all centromeres contain repeat motifs that are recognized by the DNA-binding protein. The ParA protein does not contact the centromere directly, but is instead recruited into the segrosome complex by the DNA-binding factor. Although their mode of action remains to be fully elucidated, there is growing evidence that ParA proteins can polymerize into extensive filamentous structures. Polymerization is controlled by nucleotide binding and hydrolysis, as well as by the partner protein. ParA polymerization within the segrosome could move plasmids in bipolar orientations during segregation. The tertiary structures of several partition proteins have recently been solved, providing invaluable new insights into segrosome organization and assembly. The genomes of unicellular and multicellular organisms must be partitioned equitably in coordination with cytokinesis to ensure faithful transmission of duplicated genetic material to daughter cells. Bacteria use sophisticated molecular mechanisms to guarantee accurate segregation of both plasmids and chromosomes at cell division. Plasmid segregation is most commonly mediated by a Walker-type ATPase and one of many DNA-binding proteins that assemble on a cis -acting centromere to form a nucleoprotein complex (the segrosome) that mediates intracellular plasmid transport. Bacterial chromosome segregation involves a multipartite strategy