Chelsea protein (229 residues, 28 KD) is a molecule of bracket-like decision to separate the main two subdomains, cleft by a large-scale. To form a spiral of mixed leaf b A, B, and C,, sub-domain of the N, are included until the 145-120 and 83 from the remaining one. Formation of spiral 229, D 148 and from 117 from residue 90 of the sub-domain, C is, contains the AB hairpin F, and anti-parallel B sheet and endpoints and E,. Two sub-domains is associated with a 3 polypeptide linker and, filled with the area of ​​hydrophobic residues. The connection interface provides the flexibility to enable may be two sub-domains rotate relative to each other.

Despite remarkable precision copy DNA polymerase occurs at a frequency error DNA can be measured. Lead to mutations that some errors increase the viability of organisms, many mutations are harmful. Evolved a complex system for monitoring the genome for DNA damage and mutation, choice is to repair these defects as this. The endonuclease (except SS pairs) weak base mismatch and Muth protein of E. coli is an enzyme multimeric complexes that work to repair the mismatch in different directions by one nucleotide deletions four insertion or small.

Figure 1 shows the role of Mutl and MutS of the Azimut-oriented methyl mismatch repair. After MutS, mismatch repair protein of another that is associated with the complex Mutl this time, to recognize, errors, activate the Azimut of endonuclease activity potential. Chelsea is split on one side of the gap half of methyl (GATC) sequence. Depending on the Muttokatto whether the end of the exonuclease and exonuclease VII or mismatch 5 ‘or 3’, after disgruntled gaps and final, removing portions of the DNA I, (along with the MutS of, helicase II and Mutl) will be used. Repair synthesis followed by ligation restores the wild-type sequence of double-stranded DNA. Before going on to the next section, please reload the molecule.

Chelsea active site is located in the cleft between the C-arm of the molecule and the N-side. Slit is similar to the broad and deep is the 12-14 angstroms 15-18 angstroms of restriction endonuclease many. 7 base pairs of the DNA binding cleft contact B-DNA. Glu77, Asp70 DNA binding cleft, and 79 three residues Lys is important for endonuclease cleavage. These residues have formed catalytic triad forms the D (X) 6-30 (E / D) XK. It triplets such as this is important for the catalytic activity of several enzymes constraint II are known.

The binding cleft, residues other two Phe94 and Asp91, are highly conserved. To solvent exposure completely in the free enzyme is known to feature a clear Asp91, Phe94. By probably, do you help to DNA recognition, to be inserted in between a pair of the main board, which keep the DNA in place.

Magnesium ions are required for cleavage of Muth of the target DNA sequence. Reaction of Chelsea and Mg2 + ions are the same as those of the EcoRV restriction endonuclease for displaying structural homology probably. Ions was shown to be adjusted Glu45 Hano Mg2 at EcoRV + catalysis is important. It is Glu56, is a waterborne Glu77 hydrogen bond similar to Azimut residue.

Muth, must be activated by Mutl and MutS for DNA cleavage. The exact mechanism of activation are known, but it does not seem as C-arm pivot with respect to the N-side opening and closing of the DNA-binding cleft. This is the on and off of the catalytic activity. It seems to include the C-terminal helix F. functions as a kind of molecular switch that the “push” by Mutl this spiral of the MutS, activate the Azimut of endonuclease activity potential mobile movement you may have.

Chelsea is crystallized conformation of two. The first structure, it indicates to have the F helix of AA close crack and conformation of the active enzyme is packed in tightly structure probably. Extending the solution probably has a helical structure and F more open, the second structure is a non-active form of the enzyme. The difference in packing F helix, the mascara suggests that it plays a role as a lever, which is realized by Mutl and MutS in really.

The Chelsea, a similar activity with restriction enzymes, therefore, is interested in you have a structural similarity with PvuII and significant homology with Sau3AI it. Further, as described above, the catalyst is found triad Muth Type D (X) 6-30 (E / D) XK. Eco RI, in PvuII, this motif is included in the active site of the restriction enzyme of many, including the Bam HI Eco RV, and Fok I,.

There is a big difference these enzymes. For example, a dimer Some of these, some are monomers, they show specificity for different DNA sequences. However, the presence of a motif common descended from an ancestor common proteins suggest that homologs of evolution is i.e. they. The ability of bacteria, may have evolved from the basic functions of DNA repair in order to protect from virus attacks by DNA restriction.

Chelsea and Mutl and of MutS is essential for initiation of DNA methyl directed mismatch repair to correct the errors that occur during replication of DNA in E. coli. Newly synthesized, Azimut is 5 ‘sequence of D semi-methylated double to cut the chain of methylation daughter (GATC). I need the recognition of DNA mismatch due to Mutl Azimut activation of the MutS. And sequence homology to the structural similarity of the endonuclease in PvuII and with Sau3AI, Chelsea, suggesting the descendants endonuclease thing from a common ancestor type II limit and indicates the structural similarity in the PvuII and sequence , with Sau3AI by various amendments, shows a strong relationship between these enzymes.

Of MutS, Azimut and Mutl is a major protein of three to start the methyl-directed DNA mismatch repair to correct mistakes made during DNA replication in E. coli. Newly synthesized, Azimut is 5 ‘sequence of D semi-methylated double to cut the chain of methylation daughter (GATC). I need the recognition of DNA mismatch due to Mutl Azimut activation of the MutS. We crystallizes in space group two solutions Muth resolution structure of the 2,3 and 1,7 respectively. Relative rotation to be disclosed by the comparison of the crystal structure from each other, Muth active site is located at the interface of subdomains between the two that may modulate the activity of nucleases this. Relative movement of the Chelsea of ​​two sub-domains were correlated with the position to issue a C-terminal helix. Mutl and MutS of this helix, which appears to function as a molecular lever through it that you may want to report the detection of activation Azimut and DNA mismatch. Structural similarity is related to these enzymes clearly PvuII endonuclease and has a sequence homology with Sau3AI, in Chelsea, various modifications, II type restrictions descendants endonuclease thing from a common ancestor to this I suggest.

The MutS to form a dimer (MutS2) binds to DNA that recognize mismatched base daughter strand, was mutated. Chelsea will bind hemi-methyl object along the daughter DNA, but Azimut latter and MutS2 and activates the action has not been published, and contact Mutl dimer and (MutL2) bound to the MutS-DNA complex only it functions as an intermediary between the activation. Transfer of DNA, can be in one kilobyte maximum distance in order to find the nearest D of non-compliant (GATC) methylation site. Azimut daughter strand nick UvrD helicase of the two chains of (DNA helicase II) separation near activation of MutS-DNA complexes when, ‘to 5’ 3 dial specific polarity and hemi-methyl site. In order to cut while it passes complex MutSHL across slides along the DNA in the direction of the non-release direction. The deterioration in Ekisopasu SS-DNA complex and tail. 5 ‘or 3’ – adopted exonuclease is dependent on either side of the incision where the mismatch Azimut. It was used in the case is’ (in → 3 ‘exonuclease participants made by Azimut is ExoVII or both RecJ 5), or the end of the mismatch 5’. If the participant is 3, I used the end of the “mismatch, the (enzyme ‘to 5’ 3) ExoI.

In other words, – the whole process, has been completely cut off both the nucleotide and the surrounding site to complete along the gap region. Can be a gap of one strand was created by exonuclease, as a template, by using the other strand, is removed by (assisted by element-binding protein) DNA polymerase III, and sealed by DNA ligase to a final Is the. Damumechiraze is methylated daughter strand shortly thereafter.

Mismatch repair DNA (MMR) is a pathway that is highly conserved play an important role in the maintenance of genomic stability. Specificity of the MMR is based on the generation insertion / deletion mispairs between the recombinant and DNA replication and base mismatch mainly. It suppresses homeologous recombination Further MMR, plays a role in DNA damage signaling in eukaryotic cells recently have been shown. Homolog of the eukaryotic and Mutl, MutLalpha MutSalpha and is an important player in MMR-related genome maintenance each MutS of Escherichia coli. For example, also are involved in DNA metabolism various routes, such as RPA and PCNA, protein component of many other, is essential for MMR. MMR defects is related to the whole genome instability such as abnormal predisposition and infertility division of mammals and hereditary non-polyposis colon cancer, resistant to chemotherapeutic agents particular, to cancer, some.

Repair of base base mismatch that can occur during DNA replication. Bind to a region of abnormal DNA, proteins, forming starting complex (heterodimer) thereof removed. Loss of MMR proteins accumulation of DNA replication errors in cells growing in the region of the genome in particularly short repetitive nucleotide sequence, a phenomenon known microsatellite instability as (MSI). Thus, in contrast to cell-cell, MMR deficiency of proteins within cells is associated with a high level of MSI (MSI-H) MSI low levels closely (MSI-L), the MSI stable (MSS).

Hereditary non-polyposis colon cancer (HNPCC) it is possible to be mutated in families with children (relative frequency in parentheses), in humans, 9 function MMR gene is identified, they are five: (49%) MLH1 and is a clinical concern specific PMS1 (0.3%), PMS2 (2%), MSH2 (38%), MSH6 (9%). Mutations in more than 300 have been identified. Individuals carrying mutations have MMR of normal proteins, the DNA, including parallel (loss of heterozygosity) nonmutated protein production stops if damaged. The MLH1, and hetero (MMR proteins other mutation has not been found) MLH3 or PMS2, PMS1 if MSH2 forms a complex with hetero and MSH6. If the MSH2 is insufficient, MSH6 protein is lost due to instability of the protein probably.

The repair DNA mismatches needed to maintain the stability of the genome, from prokaryotes to eukaryotes and are well preserved. Insert mismatch base pair deletions, and errors made during replication of DNA, is a substrate for mismatch repair. It is a chain-specific, mismatch repair is for the daughter strand newly synthesized only. To start the mismatch repair in E. coli, introduction of participants Mutl MutS essential, mismatch recognition, and Chelsea target direction, three proteins is mediating the interaction between MutS and Azimut. Mutl important mismatch repair and MutS homolog has been found in almost all organisms. MutS homolog of Mutl and mutations are associated with increased susceptibility to cancer in humans and mouse. In this case, the crystal structure of the nuclease Azimut, save fragments of ATP-ase Mutl (LN40), and make sure the complex of LN40 to another nucleotide. Type II restriction endonucleases and Muth has identified evolutionary relationships between the Muth established based on the crystal structure of the active site. In biochemical studies and crystal recent interaction with MutS and Mutl Single Muth has been shown to regulate by hydrolysis and ATP binding as a molecular switch. The crystal structure of these, I shed light on the general mechanism of the role of mut protein in the prevention of mutagenesis and mismatch repair.