Unraveling the structure and function of a novel SegC protein interacting with the SegAB chromosome segregation complex in Archaea.

Genome segregation is a fundamental process that preserves the genetic integrity of all organisms, but the mechanisms driving genome segregation in archaea remain enigmatic. This study delved into the unknown function of SegC (SSO0033), a novel protein thought to be involved in chromosome segregation in archaea. Using fluorescence polarization DNA binding assays, we discovered the ability of SegC to bind DNA without any sequence preference.

Chromosome segregation in Archaea: SegA- and SegB-DNA complex structures provide insights into segrosome assembly.

Genome segregation is a vital process in all organisms. Chromosome partitioning remains obscure in Archaea, the third domain of life. Here, we investigated the SegAB system from Sulfolobus solfataricus.

Genome Segregation by the Venus Flytrap Mechanism: Probing the Interaction Between the ParF ATPase and the ParG Centromere Binding Protein.

The molecular events that underpin genome segregation during bacterial cytokinesis have not been fully described. The tripartite segrosome complex that is encoded by the multiresistance plasmid TP228 in is a tractable model to decipher the steps that mediate accurate genome partitioning in bacteria. In this case, a "Venus flytrap" mechanism mediates plasmid segregation.

Combing Chromosomal DNA Mediated by the SMC Complex: Structure and Mechanisms.

Genome maintenance requires various nucleoid-associated factors in prokaryotes. Among them, the SMC (Structural Maintenance of Chromosomes) protein has been thought to play a static role in the organization and segregation of the chromosome during cell division. However, recent studies have shown that the bacterial SMC is required to align left and right arms of the emerging chromosome and that the protein dynamically travels from origin to Ter region.

A three-dimensional ParF meshwork assembles through the nucleoid to mediate plasmid segregation.

Genome segregation is a fundamental step in the life cycle of every cell. Most bacteria rely on dedicated DNA partition proteins to actively segregate chromosomes and low copy-number plasmids. Here, by employing super resolution microscopy, we establish that the ParF DNA partition protein of the ParA family assembles into a three-dimensional meshwork that uses the nucleoid as a scaffold and periodically shuttles between its poles.

Driving Apart and Segregating Genomes in Archaea.

Genome segregation is a fundamental biological process in organisms from all domains of life. How this stage of the cell cycle unfolds in Eukarya has been clearly defined and considerable progress has been made to unravel chromosome partition in Bacteria. The picture is still elusive in Archaea.

Mono-, di- and trimethylated homologues of isoprenoid tetraether lipid cores in archaea and environmental samples: mass spectrometric identification and significance.

Higher homologues of widely reported C(86) isoprenoid diglycerol tetraether lipid cores, containing 0-6 cyclopentyl rings, have been identified in (hyper)thermophilic archaea, representing up to 21% of total tetraether lipids in the cells. Liquid chromatography-tandem mass spectrometry confirms that the additional carbon atoms in the C(87-88) homologues are located in the etherified chains. Structures identified include dialkyl and monoalkyl ('H-shaped') tetraethers containing C(40-42) or C(81-82) hydrocarbons, respectively, many representing novel compounds.

Structures of archaeal DNA segregation machinery reveal bacterial and eukaryotic linkages.

Although recent studies have provided a wealth of information about archaeal biology, nothing is known about the molecular basis of DNA segregation in these organisms. Here, we unveil the machinery and assembly mechanism of the archaeal Sulfolobus pNOB8 partition system. This system uses three proteins: ParA; an atypical ParB adaptor; and a centromere-binding component, AspA.

Uncoupling of nucleotide hydrolysis and polymerization in the ParA protein superfamily disrupts DNA segregation dynamics.

DNA segregation in bacteria is mediated most frequently by proteins of the ParA superfamily that transport DNA molecules attached via the segrosome nucleoprotein complex. Segregation is governed by a cycle of ATP-induced polymerization and subsequent depolymerization of the ParA factor. Here, we establish that hyperactive ATPase variants of the ParA homolog ParF display altered segrosome dynamics that block accurate DNA segregation.

Structural mechanism of ATP-induced polymerization of the partition factor ParF: implications for DNA segregation.

Segregation of the bacterial multidrug resistance plasmid TP228 requires the centromere-binding protein ParG, the parH centromere, and the Walker box ATPase ParF. The cycling of ParF between ADP- and ATP-bound states drives TP228 partition; ATP binding stimulates ParF polymerization, which is essential for segregation, whereas ADP binding antagonizes polymerization and inhibits DNA partition. The molecular mechanism involved in this adenine nucleotide switch is unclear.

Chromosome segregation in Archaea mediated by a hybrid DNA partition machine.

Eukarya and, more recently, some bacteria have been shown to rely on a cytoskeleton-based apparatus to drive chromosome segregation. In contrast, the factors and mechanisms underpinning this fundamental process are underexplored in archaea, the third domain of life. Here we establish that the archaeon Sulfolobus solfataricus harbors a hybrid segrosome consisting of two interacting proteins, SegA and SegB, that play a key role in genome segregation in this organism.

Recruitment of the ParG segregation protein to different affinity DNA sites.

The segrosome is the nucleoprotein complex that mediates accurate plasmid segregation. In addition to its multifunctional role in segrosome assembly, the ParG protein of multiresistance plasmid TP228 is a transcriptional repressor of the parFG partition genes. ParG is a homodimeric DNA binding protein, with C-terminal regions that interlock into a ribbon-helix-helix fold.

Centromere anatomy in the multidrug-resistant pathogen Enterococcus faecium.

Multidrug-resistant variants of the opportunistic human pathogen Enterococcus have recently emerged as leading agents of nosocomial infection. The acquisition of plasmid-borne resistance genes is a driving force in antibiotic-resistance evolution in enterococci. The segregation locus of a high-level gentamicin-resistance plasmid, pGENT, in Enterococcus faecium was identified and dissected.

Promiscuous stimulation of ParF protein polymerization by heterogeneous centromere binding factors.

The segrosome is the nucleoprotein complex that mediates accurate segregation of bacterial plasmids. The segrosome of plasmid TP228 comprises ParF and ParG proteins that assemble on the parH centromere. ParF, which exemplifies one clade of the ubiquitous ParA superfamily of segregation proteins, polymerizes extensively in response to ATP binding.

The tail of the ParG DNA segregation protein remodels ParF polymers and enhances ATP hydrolysis via an arginine finger-like motif.

The ParF protein of plasmid TP228 belongs to the ubiquitous superfamily of ParA ATPases that drive DNA segregation in bacteria. ATP-bound ParF polymerizes into multistranded filaments. The partner protein ParG is dimeric, consisting of C-termini that interweave into a ribbon-helix-helix domain contacting the centromeric DNA and unstructured N-termini.

Assembling the bacterial segrosome.

Genome segregation in prokaryotes is a highly ordered process that integrates with DNA replication, cytokinesis and other fundamental facets of the bacterial cell cycle. The segrosome is the nucleoprotein complex that mediates DNA segregation in bacteria, its assembly and organization is best understood for plasmid partition. The recent elucidation of structures of the ParB plasmid segregation protein bound to centromeric DNA, and of the tertiary structures of other segregation proteins, are key milestones in the path to deciphering the molecular basis of bacterial DNA segregation.

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

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.

The unstructured N-terminal tail of ParG modulates assembly of a quaternary nucleoprotein complex in transcription repression.

ParG is the prototype of a group of small (<10 kDa) proteins involved in accurate plasmid segregation. The protein is a dimeric DNA binding factor, which consists of symmetric paired C-terminal domains that interleave into a ribbon-helix-helix fold that is crucial for the interaction with DNA, and unstructured N-terminal domains of previously unknown function. Here the ParG protein is shown to be a transcriptional repressor of the parFG genes.

Protein diversity confers specificity in plasmid segregation.

The ParG segregation protein (8.6 kDa) of multidrug resistance plasmid TP228 is a homodimeric DNA-binding factor. The ParG dimer consists of intertwined C-terminal domains that adopt a ribbon-helix-helix architecture and a pair of flexible, unstructured N-terminal tails.

Bacterial DNA segregation dynamics mediated by the polymerizing protein ParF.

Prokaryotic DNA segregation most commonly involves members of the Walker-type ParA superfamily. Here we show that the ParF partition protein specified by the TP228 plasmid is a ParA ATPase that assembles into extensive filaments in vitro. Polymerization is potentiated by ATP binding and does not require nucleotide hydrolysis.

ParG, a protein required for active partition of bacterial plasmids, has a dimeric ribbon-helix-helix structure.

The ParG protein (8.6 kDa) is an essential component of the DNA partition complex of multidrug resistance plasmid TP228. ParG is a dimer in solution, interacts with DNA sequences upstream of the parFG genes and also with the ParF partition protein both in the absence and presence of target DNA.

Architecture of the ParF*ParG protein complex involved in prokaryotic DNA segregation.

The mechanism by which low copy number plasmids are segregated at cell division involves the concerted action of two plasmid-encoded proteins that assemble on a centromere-like site. This study explores the topology of the DNA segregation machinery specified by the parFG locus of TP228, a partition system which is phylogenetically distinct from more well-characterized archetypes. A variety of genetic, biochemical and biophysical strategies revealed that the ParG protein is dimeric.