A model of structure and action of Sau3AI restriction endonuclease that comprises two MutH-like endonuclease domains within a single polypeptide.
Sau3AI is a type II endonuclease that cleaves GATC sequences, producing sticky ends with 4-nucleotide 5'-overhangs. Its activity is inhibited by cytosine C5-methylation within the target sequence. In the N-terminus, Sau3AI exhibits sequence similarity to the GATC-specific single-strand nicking endonuclease MutH implicated in mismatch repair (Ban and Yang, 1998). Sequence analysis of Sau3AI and its homologs reveals that Sau3AI possesses an additional MutH-like domain in the C-terminus. Structure prediction suggests that the C-terminal domain lacks the endonuclease active site but retains all putative DNA-binding elements. As an illustration of these findings, a model of quaternary structure of Sau3AI complexed with the target DNA is presented. These predictions have implications for evolution, structure and function of bacterial DNA repair enzymes and restriction endonucleases.
Bujnicki
J M
JM
Bioinformatics Laboratory, International Institute of Molecular and Cell Biology, Warsaw, Poland. iamb@bioinfo.pl
D000595:Amino Acid Sequence; D045643:DNA Repair Enzymes; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry / Q000235:genetics*; D004706:Endodeoxyribonucleases / Q000737:chemistry / Q000235:genetics*; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D004706:Endodeoxyribonucleases; C059682:methyl-directed mismatch repair protein, E coli; D015252:Deoxyribonucleases, Type II Site-Specific; C024405:GATC-specific type II deoxyribonucleases; D045643:DNA Repair Enzymes