Subsystem: MukBEF Chromosome Condensation

This subsystem's description is:

For more information, please check out the description and the additional notes tabs, below

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Taxonomy Pattern 
Organism 
Domain
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YcbCSmtAMukFMukEMukB
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The Following is the description of MukB from Swiss Prot
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CC -!- FUNCTION: Plays a central role in chromosome condensation,
CC segregation and cell cycle progression. Functions as a homodimer,
CC which is essential for chromosome partition. Involved in negative
CC DNA supercoiling in vivo, and by this means organize and compact
CC chromosomes. May achieve or facilitate chromosome segregation by
CC condensation DNA from both sides of a centrally located replisome
CC during cell division.
CC -!- SUBUNIT: Homodimerization via its hinge domain. Binds to DNA via
CC its C-terminal region. Interacts, and probably forms a ternary
CC complex, with mukE and mukF via its C-terminal region. The complex
CC formation is stimulated by calcium or magnesium. Interacts with
CC tubulin-related protein ftsZ. Identified in a complex with spoT;
CC iscS and ACP.
CC -!- SUBCELLULAR LOCATION: Nucleoid. Restricted to the nucleoid region.
CC -!- DOMAIN: The hinge domain, which separates the large intramolecular
CC coiled coil regions, allows the homodimerization, forming a V-
CC shaped homodimer.
CC -!- SIMILARITY: Belongs to the SMC family. MukB subfamily.

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PMID: 16368697

DNA reshaping by MukB. Right-handed knotting, left-handed supercoiling.

Petrushenko ZM, Lai CH, Rai R, Rybenkov VV.

J Biol Chem. 2006 Feb 24;281(8):4606-15. Epub 2005 Dec 20.

MukB is a bacterial SMC (structural maintenance of chromosome)
protein required for faithful chromosome segregation in Escherichia
coli. We report here that purified MukB introduces right-handed knots
into DNA in the presence of type-2 topoisomerase, indicating that the
protein promotes intramolecular DNA condensation. The pattern of
generated knots suggests that MukB, similar to eukaryotic condensins,
stabilizes large right-handed DNA loops. In contrast to eukaryotic
condensins, however, the net supercoiling stabilized by MukB was
negative. Furthermore, DNA reshaping by MukB did not require
ATP. These data establish that bacterial condensins alter the shape of
double-stranded DNA in vitro and lend support to the notions that the
right-handed knotting is the most conserved biochemical property of
condensins. Finally, we found that MukB can be eluted from a heparin
column in two distinct forms, one of which is inert in DNA binding or
reshaping. Furthermore, we find that the activity of MukB is
reversibly attenuated during chromatographic separation. Thus, MukB
has a unique set of topological properties, compared with other SMC
proteins, and is likely to exist in two different conformations.
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Swiss Prot Description of MukE

CC -!- FUNCTION: Involved in chromosome condensation, segregation and
CC cell cycle progression. May participate in facilitating chromosome
CC segregation by condensation DNA from both sides of a centrally
CC located replisome during cell division. Probably acts via its
CC interaction with mukB and mukF (By similarity).
CC -!- SUBUNIT: Interacts, and probably forms a ternary complex, with
CC mukF and mukB. The complex formation is stimulated by calcium or
CC magnesium (By similarity).
CC -!- SUBCELLULAR LOCATION: Nucleoid. Restricted to the nucleoid region.
CC -!- SIMILARITY: Belongs to the mukE family.
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Swiss Prot Description of MukF
-!- FUNCTION: Involved in chromosome condensation, segregation and
CC cell cycle progression. May participate in facilitating chromosome
CC segregation by condensation DNA from both sides of a centrally
CC located replisome during cell division. Not required for mini-F
CC plasmid partitioning. Probably acts via its interaction with mukB
CC and mukE. Overexpression results in anucleate cells. It has a
CC calcium binding activity.
CC -!- SUBUNIT: Interacts, and probably forms a ternary complex, with
CC mukE and mukB via its C-terminal region. The complex formation is
CC stimulated by calcium or magnesium. It is required for an
CC interaction between mukE and mukB.
CC -!- SUBCELLULAR LOCATION: Nucleoid. Restricted to the nucleoid region.
CC -!- SIMILARITY: Belongs to the mukF family.
CC -!- CAUTION: Was originally thought to be a killing factor. Ref.5
CC showed that it is not involved in killing system.
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SmtA:

FEMS Microbiol Lett. 1995 Nov 1;133(1-2):59-63.
Characterization of the smtA gene encoding an S-adenosylmethionine-dependent
methyltransferase of Escherichia coli.

Yamanaka K, Ogura T, Niki H, Hiraga S.

Department of Molecular Cell Biology, Kumamoto University School of Medicine, Japan.

The mukB operon is located at 21 min on the Escherichia coli chromosome and seems to consist of four genes, orf30 (smtA), mukF, mukE, and mukB. Based on sequence similarity, the promoter-proximal gene, orf30 (smtA), could encode an S-adenosylmethionine-dependent methyltransferase. The smtA gene is not essential for cell growth and its expression is positively regulated by H-NS, an Escherichia coli histone-like protein.

PMID: 8566713
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YcbC seems to be a hypothetical at this point

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