3C95

Exonuclease I (apo)

Summary for 3C95

• Entry DOI: 10.2210/pdb3c95/pdb
• Related: 1FXX 2C94
• Descriptor: Exodeoxyribonuclease I, MAGNESIUM ION (3 entities in total)
• Functional Keywords: exonuclease, ssb, genome maintenance, dna damage, dna repair, hydrolase
• Biological source: Escherichia coli
• Total number of polymer chains: 1
• Total formula weight: 55534.87

Authors

Keck, J.L.,Lu, D. (deposition date: 2008-02-15, release date: 2008-07-08, Last modification date: 2023-08-30)

Primary citation

Lu, D.,Keck, J.L.
Structural basis of Escherichia coli single-stranded DNA-binding protein stimulation of exonuclease I.
Proc.Natl.Acad.Sci.USA, 105:9169-9174, 2008

PubMed Abstract: Bacterial 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.

PubMed: 18591666
DOI: 10.1073/pnas.0800741105

Experimental method

X-RAY DIFFRACTION (1.7 Å)