|Gene:||mukB||Accession Numbers: EG10618 (EcoCyc), b0924, ECK0915|
Component of: bacterial condensin MukBEF (extended summary available)
Subunit composition of
cell division protein involved in chromosome partitioning = [MukB]2
cell division protein involved in chromosome partitioning = MukB
The MukB protein is involved in chromosome condensation and partitioning. It belongs to the family of SMC (Structural Maintenance of Chromosomes) proteins [Soppa01]. MukB acts as a macromolecular clamp that compacts DNA; condensation is cooperative, and ATP stimulates its initiation, but not propagation [Cui08]. In single-molecule observations, both MukB alone and the MukBEF complex promote shrinkage of large DNA molecules in the presence of ATP [Chen08b].
GFP-marked MukB protein is observed to occupy the same location as the nucleoid in the presence of MukE and MukF [Ohsumi01], and fluorescent antibodies also show localization to the nucleoid, but no colocalization with the FtsZ ring [denBlaauwen01]. In vivo, MukEF is required for association of MukB with the nucleoid [She07]. Mutations in the MukF linker region affect localization of MukB [Shin09a]. MukB generally colocalizes with the origin of replication (oriC) throughout the cell cylce [Danilova07], although the number of MukB foci is larger than the number of oriC foci [Adachi08a]. The oriC region is aberrantly positioned at the cell pole in a mukB mutant [Danilova07]. Sister chromatid interactions are not significantly affected in a mukB mutant [Lesterlin12].
The MukB protein forms a homodimer [Niki92]. Like other members of the SMC protein family, MukB is a large protein made up of five domains: N- and C-terminal globular "head domains", a central linker region or "hinge domain", and two coiled-coil rod domains that separate the head domains from the hinge domain. This structure can be visualized by EM; the coiled-coil regions are arranged in an antiparallel fashion in the homodimer [Melby98, Matoba05]. The relative alignment of the N- and C-terminal halves of the coiled-coil region has been investigated by site-directed crosslinking [Li09c]. Interacting pairs of residues were identified by disulfide crosslinking, revealing that five coiled-coil segments are interrupted by a novel structural motif, called a coiled-coil knuckle [Weitzel11].
The C-terminal region of MukB is essential for its DNA binding activity [Niki92, Saleh96], while the hinge domain does not appear to interact with DNA [Ku10]. ATP is not required for DNA binding [Petrushenko06]. A purified N-terminal domain of MukB binds to FtsZ in vitro [Lockhart98]. A crystal structure of the 227 N-terminal amino acid residues of MukB has been solved at 2.2 Å resolution [vandenEnt99]. Crystal structures of the central hinge domain responsible for dimerization of MukB, including a portion of the adjacent coiled-coil domain, have been solved at 3.1 and 2.3 Å resolution [Li10b, Ku10]. The hinge domain interacts directly with the C-terminal domain of ParC and stimulates the DNA relaxation and knotting activities of topoisomerase IV in vitro [Hayama10, Li10c, Hayama13], but not its decatenation activity [Hayama13]. The crystal structure of a minimal MukB-topo IV complex has been solved; the MukB hinge domain is shown to stimulate topo IV by competing for a site on its C-terminal domain that normally represses activity on negatively supercoiled DNA [Vos13].
A mukB null mutant has a cell division defect and can not form colonies [Niki91]. mukB mutants are temperature sensitive and produce anucleate cells. A mukB mutation causes unfolding of the nucleoid; this phenotype is supressed by a mutation in seqA [Weitao99, Onogi00]. Additional supressors of the mukB null mutant phenotype have been isolated in smbA [Yamanaka92], msmA, msmB, msmC [Yamanaka94a], smbB [Kido96], crcA, cspE, crcB [Hu96a], topA [Sawitzke00], and gyrB [Adachi03]. In a mukB mutant, the chromosome appears to be less supercoiled [Weitao00]. Overproduction of MukB leads to condensation of chromosomes, even in the absence of MukE and MukF [Wang06e].
Locations: cytosol, bacterial nucleoid
|Map Position: [975,549 -> 980,009] (21.03 centisomes, 76°)||Length: 4461 bp / 1486 aa|
Molecular Weight of Polypeptide: 170.23 kD (from nucleotide sequence)
Molecular Weight of Multimer: 365.0 kD (experimental) [Niki92]
Unification Links: ASAP:ABE-0003138, CGSC:31516, DIP:DIP-10273N, EchoBASE:EB0613, EcoGene:EG10618, EcoliWiki:b0924, Mint:MINT-1225884, ModBase:P22523, OU-Microarray:b0924, PortEco:mukB, PR:PRO_000023309, Pride:P22523, Protein Model Portal:P22523, RefSeq:NP_415444, RegulonDB:EG10618, SMR:P22523, String:511145.b0924, UniProt:P22523
Relationship Links: InterPro:IN-FAMILY:IPR007406, InterPro:IN-FAMILY:IPR012090, InterPro:IN-FAMILY:IPR027417, PDB:Structure:1QHL, PDB:Structure:2WMM, PDB:Structure:3IBP, PDB:Structure:4MN4, Pfam:IN-FAMILY:PF04310, Pfam:IN-FAMILY:PF13558, Pfam:IN-FAMILY:PF16330
|MultiFun Terms:||cell processes → cell division|
|Growth Medium||Growth?||T (°C)||O2||pH||Osm/L||Growth Observations|
|LB Lennox||No||37||Aerobic||7||No [Baba06, Comment 1]|
Subunit of: bacterial condensin MukBEF
Subunit composition of
bacterial condensin MukBEF = [(MukB)2][(MukE)4([MukF]2)]
cell division protein involved in chromosome partitioning = (MukB)2
cell division protein involved in chromosome partitioning = MukB
MukEF complex = (MukE)4([MukF]2) (summary available)
protein involved in chromosome partitioning = MukE (extended summary available)
MukF dimer = (MukF)2
Ca2+-binding protein involved in chromosome partitioning = MukF
Two conformations of the MukBEF complex appear to exist; the half-saturated complex, with a stoichiometry of B2(E2F)1, is relatively stable and can bind DNA, while the fully saturated MukBEF complex, with a stoichiometry of B2(E2F)2, is short-lived, unable to bind DNA and able to form multimeric complexes [Petrushenko06a].
The MukEF complex appears to compete with DNA for binding to MukB. The fully assembled MukBEF complex is unable to bind DNA; addition of MukEF to DNA-bound MukB displaces MukB from the DNA [Petrushenko06a].
Electron microscopy studies indicated that the MukE and MukF subunits of the MukBEF complex associate with the terminal globular domains of the MukB homodimer. The MukBEF complex can also be observed to form multimeric complexes in a variety of conformations [Matoba05].
It was reported that he MukBEF complex can be detected in vitro only under conditions of increased Ca2+ or Mg2+ concentration [Yamazoe99]; however, [Matoba05] was able to purify the complex in the absence of ions.
|Feature Class||Location||Attached Group||Citations||Comment|
|Nucleotide-Phosphate-Binding-Region||34 -> 41||ATP|
|Sequence-Conflict||318 -> 319|
|Protein-Segment||645 -> 804|
|Protein-Segment||666 -> 783|
|Sequence-Conflict||1174 -> 1175|
|Sequence-Conflict||1276 -> 1277|
|Sequence-Conflict||1357 -> 1380|
|Sequence-Conflict||1390 -> 1486|
|Pfam PF04310||2 -> 227|
|Pfam PF16330||645 -> 810|
|Pfam PF13558||1336 -> 1424|
10/20/97 Gene b0924 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10618; confirmed by SwissProt match.
Baba06: Baba T, Ara T, Hasegawa M, Takai Y, Okumura Y, Baba M, Datsenko KA, Tomita M, Wanner BL, Mori H (2006). "Construction of Escherichia coli K-12 in-frame, single-gene knockout mutants: the Keio collection." Mol Syst Biol 2;2006.0008. PMID: 16738554
Butland05: Butland G, Peregrin-Alvarez JM, Li J, Yang W, Yang X, Canadien V, Starostine A, Richards D, Beattie B, Krogan N, Davey M, Parkinson J, Greenblatt J, Emili A (2005). "Interaction network containing conserved and essential protein complexes in Escherichia coli." Nature 433(7025);531-7. PMID: 15690043
Case04: Case RB, Chang YP, Smith SB, Gore J, Cozzarelli NR, Bustamante C (2004). "The bacterial condensin MukBEF compacts DNA into a repetitive, stable structure." Science 305(5681);222-7. PMID: 15178751
Chen08b: Chen N, Zinchenko AA, Yoshikawa Y, Araki S, Adachi S, Yamazoe M, Hiraga S, Yoshikawa K (2008). "ATP-induced shrinkage of DNA with MukB protein and the MukBEF complex of Escherichia coli." J Bacteriol 190(10);3731-7. PMID: 18326568
Danilova07: Danilova O, Reyes-Lamothe R, Pinskaya M, Sherratt D, Possoz C (2007). "MukB colocalizes with the oriC region and is required for organization of the two Escherichia coli chromosome arms into separate cell halves." Mol Microbiol 65(6);1485-92. PMID: 17824928
denBlaauwen01: den Blaauwen T, Lindqvist A, L?we J, Nanninga N (2001). "Distribution of the Escherichia coli structural maintenance of chromosomes (SMC)-like protein MukB in the cell." Mol Microbiol 42(5);1179-88. PMID: 11886550
DiazMejia09: Diaz-Mejia JJ, Babu M, Emili A (2009). "Computational and experimental approaches to chart the Escherichia coli cell-envelope-associated proteome and interactome." FEMS Microbiol Rev 33(1);66-97. PMID: 19054114
Finn14: Finn RD, Bateman A, Clements J, Coggill P, Eberhardt RY, Eddy SR, Heger A, Hetherington K, Holm L, Mistry J, Sonnhammer EL, Tate J, Punta M (2014). "Pfam: the protein families database." Nucleic Acids Res 42(Database issue);D222-30. PMID: 24288371
Hayama10: Hayama R, Marians KJ (2010). "Physical and functional interaction between the condensin MukB and the decatenase topoisomerase IV in Escherichia coli." Proc Natl Acad Sci U S A 107(44);18826-31. PMID: 20696938
Hayama13: Hayama R, Bahng S, Karasu ME, Marians KJ (2013). "The MukB-ParC interaction affects the intramolecular, not intermolecular, activities of topoisomerase IV." J Biol Chem 288(11);7653-61. PMID: 23349462
Hu96a: Hu KH, Liu E, Dean K, Gingras M, DeGraff W, Trun NJ (1996). "Overproduction of three genes leads to camphor resistance and chromosome condensation in Escherichia coli." Genetics 143(4);1521-32. PMID: 8844142
Kido96: Kido M, Yamanaka K, Mitani T, Niki H, Ogura T, Hiraga S (1996). "RNase E polypeptides lacking a carboxyl-terminal half suppress a mukB mutation in Escherichia coli." J Bacteriol 178(13);3917-25. PMID: 8682798
Li09c: Li Y, Weitzel CS, Arnold RJ, Oakley MG (2009). "Identification of interacting regions within the coiled coil of the Escherichia coli structural maintenance of chromosomes protein MukB." J Mol Biol 391(1);57-73. PMID: 19482037
Li10b: Li Y, Schoeffler AJ, Berger JM, Oakley MG (2010). "The crystal structure of the hinge domain of the Escherichia coli structural maintenance of chromosomes protein MukB." J Mol Biol 395(1);11-9. PMID: 19853611
Li10c: Li Y, Stewart NK, Berger AJ, Vos S, Schoeffler AJ, Berger JM, Chait BT, Oakley MG (2010). "Escherichia coli condensin MukB stimulates topoisomerase IV activity by a direct physical interaction." Proc Natl Acad Sci U S A 107(44);18832-7. PMID: 20921377
Luijsterburg06: Luijsterburg MS, Noom MC, Wuite GJ, Dame RT (2006). "The architectural role of nucleoid-associated proteins in the organization of bacterial chromatin: a molecular perspective." J Struct Biol 156(2);262-72. PMID: 16879983
Matoba05: Matoba K, Yamazoe M, Mayanagi K, Morikawa K, Hiraga S (2005). "Comparison of MukB homodimer versus MukBEF complex molecular architectures by electron microscopy reveals a higher-order multimerization." Biochem Biophys Res Commun 333(3);694-702. PMID: 15979051
Melby98: Melby TE, Ciampaglio CN, Briscoe G, Erickson HP (1998). "The symmetrical structure of structural maintenance of chromosomes (SMC) and MukB proteins: long, antiparallel coiled coils, folded at a flexible hinge." J Cell Biol 142(6);1595-604. PMID: 9744887
Niki91: Niki H, Jaffe A, Imamura R, Ogura T, Hiraga S (1991). "The new gene mukB codes for a 177 kd protein with coiled-coil domains involved in chromosome partitioning of E. coli." EMBO J 10(1);183-93. PMID: 1989883
Niki92: Niki H, Imamura R, Kitaoka M, Yamanaka K, Ogura T, Hiraga S (1992). "E.coli MukB protein involved in chromosome partition forms a homodimer with a rod-and-hinge structure having DNA binding and ATP/GTP binding activities." EMBO J 11(13);5101-9. PMID: 1464330
Ohsumi01: Ohsumi K, Yamazoe M, Hiraga S (2001). "Different localization of SeqA-bound nascent DNA clusters and MukF-MukE-MukB complex in Escherichia coli cells." Mol Microbiol 40(4);835-45. PMID: 11401691
Onogi00: Onogi T, Yamazoe M, Ichinose C, Niki H, Hiraga S (2000). "Null mutation of the dam or seqA gene suppresses temperature-sensitive lethality but not hypersensitivity to novobiocin of muk null mutants." J Bacteriol 182(20);5898-901. PMID: 11004192
Saleh96: Saleh AZ, Yamanaka K, Niki H, Ogura T, Yamazoe M, Hiraga S (1996). "Carboxyl terminal region of the MukB protein in Escherichia coli is essential for DNA binding activity." FEMS Microbiol Lett 143(2-3);211-6. PMID: 8837474
Sawitzke00: Sawitzke JA, Austin S (2000). "Suppression of chromosome segregation defects of Escherichia coli muk mutants by mutations in topoisomerase I." Proc Natl Acad Sci U S A 97(4);1671-6. PMID: 10660686
Soppa01: Soppa J (2001). "Prokaryotic structural maintenance of chromosomes (SMC) proteins: distribution, phylogeny, and comparison with MukBs and additional prokaryotic and eukaryotic coiled-coil proteins." Gene 278(1-2);253-64. PMID: 11707343
vandenEnt99: van den Ent F, Lockhart A, Kendrick-Jones J, L?we J (1999). "Crystal structure of the N-terminal domain of MukB: a protein involved in chromosome partitioning." Structure Fold Des 7(10);1181-7. PMID: 10545328
Weitao99: Weitao T, Nordstr?m K, Dasgupta S (1999). "Mutual suppression of mukB and seqA phenotypes might arise from their opposing influences on the Escherichia coli nucleoid structure." Mol Microbiol 34(1);157-68. PMID: 10540294
Yamanaka92: Yamanaka K, Ogura T, Niki H, Hiraga S (1992). "Identification and characterization of the smbA gene, a suppressor of the mukB null mutant of Escherichia coli." J Bacteriol 174(23);7517-26. PMID: 1447125
Yamanaka94a: Yamanaka K, Mitani T, Ogura T, Niki H, Hiraga S (1994). "Cloning, sequencing, and characterization of multicopy suppressors of a mukB mutation in Escherichia coli." Mol Microbiol 1994;13(2);301-12. PMID: 7984109
Yamanaka94b: Yamanaka K, Mitani T, Feng J, Ogura T, Niki H, Hiraga S (1994). "Two mutant alleles of mukB, a gene essential for chromosome partition in Escherichia coli." FEMS Microbiol Lett 123(1-2);27-31. PMID: 7988894
Yamanaka95: Yamanaka K, Ogura T, Niki H, Hiraga S (1995). "Characterization of the smtA gene encoding an S-adenosylmethionine-dependent methyltransferase of Escherichia coli." FEMS Microbiol Lett 1995;133(1-2);59-63. PMID: 8566713
Yamanaka96: Yamanaka K, Ogura T, Niki H, Hiraga S (1996). "Identification of two new genes, mukE and mukF, involved in chromosome partitioning in Escherichia coli." Mol Gen Genet 1996;250(3);241-51. PMID: 8602138
Yamazoe99: Yamazoe M, Onogi T, Sunako Y, Niki H, Yamanaka K, Ichimura T, Hiraga S (1999). "Complex formation of MukB, MukE and MukF proteins involved in chromosome partitioning in Escherichia coli." EMBO J 18(21);5873-84. PMID: 10545099
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