MutH is an endonuclease very weak is activated when it is bound to the (bound to MutS forthcoming) Mutl. Non-methylated DNA and he Nick unmethylated DNA strand hemimethylated, DNA is not fully methylated participants. If the chains which is methylated experimentally, that the gap repair is random is found to it. These actions led to the proposal that the Azimut to determine the circuit including a mismatch. The N Azimut a homolog of eukaryotic organisms at all. The endonuclease, its function is taken over by Mutl homolog having the specific 5′-3 ‘exonuclease activity of some. In eukaryotes, the distance from the bias to eliminate inconsistencies daughter strand newly synthesized may be provided by free 3 ‘end of the Okazaki fragments in a new field that is created during replication.


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.