The Bacterial Paradigm
Reconstituted with in vitro completely paradigm of bacteria, the JE MMR system includes a protein of one particular 3: MutS of the Azimut and Mutl. Of MutS is a mismatch recognition ATP-ase, of the effect, the couple mismatch recognition by MutS intermediate processing stage of the ATP-ase,, Mutl is Azimut Endonuclease for the repair of DNA strand is synthesized methylation-sensitive new. MutS proteins bind to DNA as shown in the specific homodimer in vitro of base mispairs and base , length loops to 4 nucleotide (NT). Deletion analysis I have shown that the MutS N-terminal of the contrast is essential for binding comprising a mismatch, C-terminus of the protein are involved in dimerization DNA.
It is a P-loop motif for binding triphosphate nucleoside I encourage half of the binding / hydrolysis of ATP and MutS of the C-terminus of the dissociation Step complex MutS-mismatch appears to be essential for downstream of MMR. Mutant retained ATP-binding domain of MutS of Cause is bound to eliminate irreversible discrepancy probably is associated with a dominant negative mutator phenotype in vivo Link a competent repair complex. As visualized by electron microscopy, Trigger, add the ATP of the formation of the complex MutS mismatch binding Mismatch between the structure and MutS at the base of the form loop loop Top. Modri ch have proposed that this structure is generated From ATP hydrolysis according to the two-way transfer of MutS in Mismatch.
Was the crystal structure (W & P Xie Yang, personal communication), of each complex MutS dimer of T. Aqua (T Sixma, personal communication) and MutS dimer of Escherichia coli and oligonucleotides containing mismatches Has been resolved. Structure are very similar and provide insight protein invaluable Function. Although both of these proteins function as subunit homodimers, the monomeric I have different units. It is essential in the formation of the heterodimer subunits of the same structure of the protein, from an evolutionary perspective As he explained the reason for existence as a hetero only of eukaryotic MutS complex. Crystal structure shows that it has one of the MutS two grooves Represents the mismatch binding site, and includes the identification saved phenylalanine in the previous cross-linking study. The 1 subunit is actually
Both in the form of DNA clamp, binds the mismatch. The crystal structure confirms the helix-turn-helix domain that is highly conserved At the end, as shows, and is important for dimerization of it of MutS, the DNA-binding site and ATP-ase site is a complex site that uses domain Both subunits. According to the complex nature of the site break like this Dimerization, simultaneous loss helix-turn-helix domain result of ATP (WYang P and Xie, personal communication) bond mismatch and hydrolysis. Direction discrimination of signals in E. coli MMR system provided by Transition state of the non-methylated DNA newly synthesized.
In particular, it marks the strands broken to re-synthesis and exonuclease removal as this, Azimut protein cleaves the unmethylated strand of the hemi-site GATC Dam methylation. Mismatch of the dependent section and Chelsea, It is activated in vitro by a complex of MutS non DNA.Because and Mutl is, are stalling the exonuclease specific endonuclease activity, active UvrD of (Mutu) helicase, to unwind the molecule of double is required. Undoing in the UvrD helicase to start earning participants and in a direct way to the contradiction. Nature of methyl-oriented E. coli system, is an effective way to distinguish the daughter strand templates and DNA replication at the time of MMR, but this mechanism is universal in prokaryotes, (see below) eukaryotes It does not apply obviously. In the absence of active Muth, existing participant of one strand of the duplex is sufficient to duplex-specific repair in vitro.
Thing for MMR, however, genetic research is essential as opposed to Mutl has been shown MutS protein with Muth to determine was difficult its precise role in MMR. The N-terminal region of the protein family Mutl is well preserved, and is included Dimerization region ATP binding / hydrolysis area, of Mutl I seem to be present in the C-terminal region of the protein. The crystallographic studies, the ATP binding leads to dimerization of the N-terminus has been shown Part of the protein, as well as structural changes It was speculated that play an important role in adjusting the initial stage of mismatch recognition to downstream processing. The Mutl, that interact in this way is expected to MMR and multiple components.
It is shown using the analysis and affinity purification of Delete a direct interaction between the MutS with Mutl of the MutS C-terminal region is shown to be important for Mutl-MutS interaction . In addition MutS interaction Mutl-between, the direct interaction,
It is Mutl C-terminal region of Azimut and Mutl only has been proven To stimulate the Azimut of endonuclease activity has been shown. C-terminal Interacts with UvrD directly and Mutl area, participated in the activation Helicase activity of this protein. Mutl guess to load the UvrD In a direct way, because helicase participants, DNA development revenue Diverge. The overall pattern that emerges from the biochemical study Mutl coordinate mismatch binding activity of MutS it with Chelsea UvrD helicase activity and cutting, and therefore direct removal circuit process.