Segrosomes are
protein complex
A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multidomain enzymes, in which multiple active site, catalytic domains are found in a single polypeptide chain.
...
es that ensure accurate segregation (partitioning) of
plasmid
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria and ...
s or
chromosome
A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...
s during
bacterial cell division.
Just as higher forms of life have evolved a complex
mitotic
Mitosis () is a part of the cell cycle in eukaryotic cells in which replicated chromosomes are separated into two new nuclei. Cell division by mitosis is an equational division which gives rise to genetically identical cells in which the t ...
apparatus to partition duplicated
DNA
Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...
during
cell division
Cell division is the process by which a parent cell (biology), cell divides into two daughter cells. Cell division usually occurs as part of a larger cell cycle in which the cell grows and replicates its chromosome(s) before dividing. In eukar ...
,
bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
require a specialized apparatus to partition their duplicated DNA. In bacteria, segrosomes perform the function similar to that performed by
mitotic spindle
In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells. It is referred to as the mitotic spindle during mitosis, a process ...
. Therefore, segrosomes can be thought of as minimalist spindles.
Segrosomes are usually composed of three basic components- the DNA (plasmid or chromosome) that needs to be segregated into daughter cells, a motor protein that provides the necessary physical forces for accomplishing the segregation and a DNA binding protein that connects the DNA and the motor protein, to form the complete segrosome complex.
Motor proteins present in bacterial segrosomal complexes
The majority of motor proteins participating in plasmid segrosomes are Walker-type or ParM type
ATPase
ATPases (, Adenosine 5'-TriPhosphatase, adenylpyrophosphatase, ATP monophosphatase, triphosphatase, ATP hydrolase, adenosine triphosphatase) are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion or ...
s. Segrosome formation could be a highly regulated and ordered process to ensure its coupling with the other events of the bacterial cell cycle. Recently segrosomal complexes derived from the tubulin family of
cytoskeletal proteins, which are
GTPase
GTPases are a large family of hydrolase enzymes that bind to the nucleotide guanosine triphosphate (GTP) and hydrolyze it to guanosine diphosphate (GDP). The GTP binding and hydrolysis takes place in the highly conserved P-loop "G domain", a ...
s have been discovered in megaplasmids found in ''
Bacillus
''Bacillus'', from Latin "bacillus", meaning "little staff, wand", is a genus of Gram-positive, rod-shaped bacteria, a member of the phylum ''Bacillota'', with 266 named species. The term is also used to describe the shape (rod) of other so-sh ...
'' species.
See also
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Plasmid
A plasmid is a small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently. They are most commonly found as small circular, double-stranded DNA molecules in bacteria and ...
*
Bacteria
Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
*
FtsZ
FtsZ is a protein encoded by the ''ftsZ'' gene that assembles into a ring at the future site of bacterial cell division (also called the Z ring). FtsZ is a prokaryotic homologue of the eukaryotic protein tubulin. The initials FtsZ mean "Filame ...
*
Tubulin
Tubulin in molecular biology can refer either to the tubulin protein superfamily of globular proteins, or one of the member proteins of that superfamily. α- and β-tubulins polymerize into microtubules, a major component of the eukaryotic cytosk ...
References
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* {{cite journal , last1 = Anand , first1 = SP , last2 = Akhtar , first2 = P , last3 = Tinsley , first3 = E , last4 = Watkins , first4 = SC , last5 = Khan , first5 = SA , date = Feb 2008 , title = GTP-dependent polymerization of the tubulin-like RepX replication protein encoded by the pXO1 plasmid of Bacillus anthracis , journal = Mol Microbiol , volume = 67 , issue = 4, pages = 881–90 , doi=10.1111/j.1365-2958.2007.06100.x, pmid = 18179418 , doi-access = free
Cell biology