Thermus thermophilus MutS2, a MutS paralogue, possesses an endonuclease activity promoted by MutL.
The mismatch repair system (MMR) recognizes and corrects mismatched or unpaired bases caused mainly by DNA polymerase, and contributes to the fidelity of DNA replication in living cells. In Escherichia coli, the MutHLS system is known to function in MMR, and homologues of MutS and MutL are widely conserved in almost all organisms. However, the MutH endonuclease has not been found in the majority of organisms. Such organisms, including Thermus thermophilus HB8, often possess the so-called MutS2 protein, which is highly homologous to MutS but contains an extra C-terminal stretch. To elucidate the function of MutS2, we overexpressed and purified T. thermophilus MutS2 (ttMutS2). ttMutS2 demonstrated the ability to bind double-stranded (ds) DNA, but, unlike ttMutS, ttMutS2 showed no specificity for mismatched duplexes. ttMutS2 ATPase activity was also detected and was stimulated by dsDNA. Our results also showed that ttMutS2 incises dsDNA. ttMutS2 incises not only oligo dsDNA but also plasmid DNA, suggesting that ttMutS2 possesses an endonuclease activity. At low concentrations, the incision activity was not retained, but was promoted by T. thermophilus MutL.
Fukui
Kenji
K
Department of Biology, Graduate School of Science, Osaka University, 1-1 Machikaneyamacho, Toyonaka, Osaka 560-0043.
Masui
Ryoji
R
Kuramitsu
Seiki
S
D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D020137:Base Pair Mismatch; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D045643:DNA Repair Enzymes / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D019281:Dimerization; D004720:Endonucleases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D058619:Maltose-Binding Proteins; D008969:Molecular Sequence Data; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; D009841:Oligonucleotides / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology* / Q000235:genetics
D001426:Bacterial Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D058619:Maltose-Binding Proteins; C074770:MutL protein, E coli; D009841:Oligonucleotides; D011993:Recombinant Fusion Proteins; D004247:DNA; D004720:Endonucleases; D000251:Adenosine Triphosphatases; D000070956:MutL Proteins; D051719:MutS DNA Mismatch-Binding Protein; C497175:MutS protein, E coli; D045643:DNA Repair Enzymes