3c95
Exonuclease I (apo)
Structural highlights
FunctionEX1_ECOLI Also functions as a DNA deoxyribophosphodiesterase that releases deoxyribose-phosphate moieties following the cleavage DNA at an apurinic/apyrimidinic (AP) site by either an AP endonuclease AP lyase. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedBacterial single-stranded DNA (ssDNA)-binding proteins (SSBs) play essential protective roles in genome biology by shielding ssDNA from damage and preventing spurious DNA annealing. Far from being inert, ssDNA/SSB complexes are dynamic DNA processing centers where many different enzymes gain access to genomic substrates by exploiting direct interactions with SSB. In all cases examined to date, the C terminus of SSB (SSB-Ct) forms the docking site for heterologous proteins. We describe the 2.7-A-resolution crystal structure of a complex formed between a peptide comprising the SSB-Ct element and exonuclease I (ExoI) from Escherichia coli. Two SSB-Ct peptides bind to adjacent sites on ExoI. Mutagenesis studies indicate that one of these sites is important for association with the SSB-Ct peptide in solution and for SSB stimulation of ExoI activity, whereas the second has no discernable function. These studies identify a correlation between the stability of the ExoI/SSB-Ct complex and SSB-stimulation of ExoI activity. Furthermore, mutations within SSB's C terminus produce variants that fail to stimulate ExoI activity, whereas the SSB-Ct peptide alone has no effect. Together, our findings indicate that SSB stimulates ExoI by recruiting the enzyme to its substrate and provide a structural paradigm for understanding SSB's organizational role in genome maintenance. Structural basis of Escherichia coli single-stranded DNA-binding protein stimulation of exonuclease I.,Lu D, Keck JL Proc Natl Acad Sci U S A. 2008 Jul 8;105(27):9169-74. Epub 2008 Jun 30. PMID:18591666[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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