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The phage gene 52 protein shares homology with the bacterial gyrase gyrA subunit [18] and the phage gene 39 protein shares homology with the gyrB subunit. [19] Since the host E. coli DNA gyrase can partially compensate for the loss of the phage gene products, mutants defective in either genes 39, 52 or 60 do not completely abolish phage DNA ...
Bacteroides is a genus of Gram-negative, obligate anaerobic bacteria. Bacteroides species are non endospore–forming bacilli, and may be either motile or nonmotile, depending on the species. [3] The DNA base composition is 40–48% GC. Unusual in bacterial organisms, Bacteroides membranes contain sphingolipids.
With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound. [43] If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together.
A negatively supercoiled DNA molecule will produce either a one-start left-handed helix, the toroid, or a two-start right-handed helix with terminal loops, the plectoneme. Plectonemes are typically more common in nature, and this is the shape most bacterial plasmids will take. For larger molecules it is common for hybrid structures to form ...
Across all forms of life, DNA gyrase is the only topoisomerase that can create negative supercoiling and it is because of this unique ability that bacterial genomes possess free negative supercoils; DNA gyrase is found in all bacteria but absent from higher eukaryotes.
The diagram shows the effects of nicks on intersecting DNA in a twisted plasmid. Nicking can be used to dissipate the energy held up by intersecting states. The nicks allow the DNA to take on a circular shape. [2] The diagram shows the effects of nicks on intersecting DNA forms. A plasmid is tightly wound into a negative supercoil (a).
The E. Coli DnaG primase is a 581 residue monomeric protein with three functional domains, according to proteolysis studies. There is an N-terminal Zinc-binding domain (residues 1–110) where a zinc ion is tetrahedrally coordinated between one histidine and three cysteine residues, which plays a role in recognizing sequence specific DNA binding sites.
HU is a small (10 kDa [12]) bacterial DNA-binding protein, which structurally differs from a eukaryotic histone but functionally acts similarly to a histone by inducing negative supercoiling into circular DNA with the assistance of topoisomerase. The protein has been implicated in DNA replication, recombination, and repair.