|Gene:||mutH||Accession Numbers: EG10624 (MetaCyc), b2831, ECK2827|
Synonyms: mutR, prv
Species: Escherichia coli K-12 substr. MG1655
Component of: MutHLS complex, methyl-directed mismatch repair (extended summary available)
The crystal structure of MutH has been determined in two space groups and solved the structures at 1.7 and 2.3 Å resolution, respectively [Ban98].
Transcription of mutH might be negatively regulated by sigma38 through an intermediate regulator as shown in [Tsui97].
|Map Position: [2,967,684 -> 2,968,373]|
Molecular Weight of Polypeptide: 25.527 kD (from nucleotide sequence)
Unification Links: ASAP:ABE-0009287 , CGSC:471 , DIP:DIP-10284N , EchoBASE:EB0619 , EcoGene:EG10624 , EcoliWiki:b2831 , Mint:MINT-1542547 , ModBase:P06722 , OU-Microarray:b2831 , PortEco:mutH , PR:PRO_000023323 , Protein Model Portal:P06722 , RefSeq:NP_417308 , RegulonDB:EG10624 , SMR:P06722 , String:511145.b2831 , UniProt:P06722
Relationship Links: InterPro:IN-FAMILY:IPR004230 , InterPro:IN-FAMILY:IPR011335 , InterPro:IN-FAMILY:IPR011337 , PDB:Structure:1AZO , PDB:Structure:2AZO , Pfam:IN-FAMILY:PF02976 , Smart:IN-FAMILY:SM00927
|Biological Process:||GO:0000018 - regulation of DNA recombination
GO:0006298 - mismatch repair [Junop03, Lahue89, Glickman80]
GO:0090305 - nucleic acid phosphodiester bond hydrolysis [Welsh87, Junop03, UniProtGOA11a, GOA01a]
GO:0006281 - DNA repair [UniProtGOA11a]
GO:0006304 - DNA modification [GOA01a]
GO:0006974 - cellular response to DNA damage stimulus [UniProtGOA11a]
|Molecular Function:||GO:0003677 - DNA binding
GO:0004519 - endonuclease activity [UniProtGOA11a, GOA01a, Au92, Welsh87]
GO:0005515 - protein binding [Polosina09, Mansour01, Hall99a]
GO:0043765 - T/G mismatch-specific endonuclease activity [Junop03]
GO:0004518 - nuclease activity [UniProtGOA11a]
GO:0016787 - hydrolase activity [UniProtGOA11a]
|Cellular Component:||GO:0032300 - mismatch repair complex
GO:0005737 - cytoplasm [UniProtGOA11, UniProtGOA11a]
GO:0005829 - cytosol [DiazMejia09]
|MultiFun Terms:||information transfer → DNA related → DNA repair|
Subunit of: MutHLS complex, methyl-directed mismatch repair
Species: Escherichia coli K-12 substr. MG1655
Subunit composition of MutHLS complex, methyl-directed mismatch repair = [MutL][MutS][MutH]
Mismatched base pairs in Escherichia coli can arise from a number of processes including replication errors, formation of heteroduplexes during recombination events and deamination of 5-methylcytosine. Multiple pathways exist to repair mismatches and one of the challenges these pathways face is in choosing which one of the two bases in the mismatch represents the "correct" DNA and which needs to be repaired. The pathways can be divided into "generalized" and "specific" pathways. Examples of the specific pathways include very short patch (VSP) repair, G:U (MUG) mismatch repair, and MutY based excision repair.
Generalized methyl-directed mismatch repair targets base-base mismatches such as G:T and insertion/deletion loops (IDLs) that cause frameshifts [Schofield03, Au92]. The methyl-directed mismatch repair system (also known as the MutHLS-dependent mismatch repair system) recognizes most base-base mispairs, as well as mismatches involving a small number of nucleotide insertion-deletions [Au92].
The selection of which strand to excise is guided by a methylation system in which newly replicated DNA is unmethylated and therefore sensitive to MutH endonuclease. In the first step MutS binds to the mismatch or IDL and to ATP [Su86, Schofield01]. MutS then recruits MutL and together they activate MutH which then preferentially cleaves the unmethylated strand (the strand with the mismatch) at hemimethylated dGATC sites. The nick at the dGATC site serves as a point of entry for single-stranded DNA binding protein (SSB) and helicase II. Mismatch repair is bidirectional in that the dGATC site can be located on either side of the mismatch and as far as 1kb away. The excision reaction requires either the 3' to 5' exonuclease activity of Exonuclease I or Exonuclease X if the unmethylated GATC site is 3' to the mismatch or the 5' to 3' exonuclease activity of exonuclease VII or RecJ exonuclease if the unmethylated GATC site is 5' to the mismatch [Schofield03, Cooper93]. DNA helicase II (the uvrD gene product) is thought to function to displace the incised strand, rendering it sensitive to attack by the exonuclease [Grilley93]. Hydrolysis thus commences at the dGATC terminus and proceeds to a point beyond the mismatch followed by resynthesis of the excised strand by DNA polymerase III and then ligation by DNA ligase.
Mutation deletion studies of UV radiation-sensitive mutants revealed several genes of importance in the methyl-directed pathway including mutH, mutL, mutS and uvrD, or DNA helicase II. Purification and reconstitution studies [Cooper93] showed that, in addition to these enzymes, single strand DNA-binding protein (SSB), DNA polymerase III, exonuclease I (the sbcB+ gene product), exonuclease VII (the xse+ gene product), RecJ exonuclease, DNA ligase, ATP, the four deoxynucleoside triphosphates and NAD+ are all also required [Grilley93]. MutH was found to be a dGATC endonuclease but only in the course of methyl-directed mismatch activation in the presence of MutL, MutS, ATP and a divalent cation [Welsh87, Au92].
Enzymatic reaction of: methyl-directed mismatch repair
The reaction direction shown, that is, A + B ↔ C + D versus C + D ↔ A + B, is in accordance with the direction in which it was curated.
Reversibility of this reaction is unspecified.
The selection of which strand to excise is guided by a methylation system in which newly replicated DNA is unmethylated and therefore sensitive to MutH endonuclease. In the first step MutS binds to the mismatch or IDL and to ATP [Schofield01]. MutS then recruits MutL and together they activate MutH which then preferentially cleaves the unmethylated strand (the strand with the mismatch) at hemimethylated dGATC sites. The nick at the dGATC site serves as a point of entry for single-stranded DNA binding protein (SSB) and helicase II
|Chain||2 -> 229|
10/20/97 Gene b2831 from Blattner lab Genbank (v. M52) entry merged into EcoCyc gene EG10624; confirmed by SwissProt match.
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
Hall99a: Hall MC, Matson SW (1999). "The Escherichia coli MutL protein physically interacts with MutH and stimulates the MutH-associated endonuclease activity." J Biol Chem 274(3);1306-12. PMID: 9880500
Hura13: Hura GL, Tsai CL, Claridge SA, Mendillo ML, Smith JM, Williams GJ, Mastroianni AJ, Alivisatos AP, Putnam CD, Kolodner RD, Tainer JA (2013). "DNA conformations in mismatch repair probed in solution by X-ray scattering from gold nanocrystals." Proc Natl Acad Sci U S A 110(43);17308-13. PMID: 24101514
Junop03: Junop MS, Yang W, Funchain P, Clendenin W, Miller JH (2003). "In vitro and in vivo studies of MutS, MutL and MutH mutants: correlation of mismatch repair and DNA recombination." DNA Repair (Amst) 2(4);387-405. PMID: 12606120
Mansour01: Mansour CA, Doiron KM, Cupples CG (2001). "Characterization of functional interactions among the Escherichia coli mismatch repair proteins using a bacterial two-hybrid assay." Mutat Res 485(4);331-8. PMID: 11585365
Polosina09: Polosina YY, Mui J, Pitsikas P, Cupples CG (2009). "The Escherichia coli mismatch repair protein MutL recruits the Vsr and MutH endonucleases in response to DNA damage." J Bacteriol 191(12);4041-3. PMID: 19376855
Rayssiguier89: Rayssiguier C, Thaler DS, Radman M (1989). "The barrier to recombination between Escherichia coli and Salmonella typhimurium is disrupted in mismatch-repair mutants." Nature 342(6248);396-401. PMID: 2555716
Tsui97: Tsui HC, Feng G, Winkler ME (1997). "Negative regulation of mutS and mutH repair gene expression by the Hfq and RpoS global regulators of Escherichia coli K-12." J Bacteriol 179(23);7476-87. PMID: 9393714
Wang03c: Wang H, Yang Y, Schofield MJ, Du C, Fridman Y, Lee SD, Larson ED, Drummond JT, Alani E, Hsieh P, Erie DA (2003). "DNA bending and unbending by MutS govern mismatch recognition and specificity." Proc Natl Acad Sci U S A 100(25);14822-7. PMID: 14634210
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