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Metal binding at the Deinococcus radiodurans Dps-1 N-terminal metal site controls dodecameric assembly and DNA binding.
MedLine Citation:
PMID:  22846100     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The prokaryotic DNA protection during starvation (Dps) proteins typically protect macromolecules against damaging agents via physical association with DNA and by oxidizing and sequestering iron. However, Deinococcus radiodurans Dps-1, which binds DNA with high affinity, fails to protect DNA against hydroxyl radicals due to iron leakage from the core, raising the question of how OH-mediated damage to Dps-1-bound DNA is avoided. As shown here, Mn(II) inhibits ferroxidase activity, suggesting that ferroxidation may be prevented in vivo as D. radiodurans accumulates a high ratio of Mn:Fe. Dps-1 has an N-terminal extension with a unique metal-binding site, an extension that has been proposed to be important for DNA binding and dodecameric assembly. Electrophoretic mobility shift assays show that Mn(II) restores DNA binding to bipyridyl-treated Dps-1, whereas Fe(II) fails to do so in the presence of H2O2, thus preventing DNA binding under conditions of ongoing ferroxidase activity. We also show that disruption of the N-terminal metal site leads to a significant reduction in DNA binding and to compromised oligomeric assembly, with the mutant protein assembling into a hexamer in the presence of divalent metal. We propose that securing the N-terminal loop by metal-binding is required to initiate dodecameric assembly by contacting the neighboring dimer, and that the absence of such optimal contacts results in formation of a hexameric assembly intermediate in which three dimers associate about one of the three-fold axes. Once dodecameric Dps-1 is assembled, metal-binding no longer affects oligomeric state; instead, differential metal-binding controls DNA interaction under conditions of oxidative stress.
Authors:
Khoa Huynh Nguyen; Anne Grove
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-7-31
Journal Detail:
Title:  Biochemistry     Volume:  -     ISSN:  1520-4995     ISO Abbreviation:  -     Publication Date:  2012 Jul 
Date Detail:
Created Date:  2012-7-31     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0370623     Medline TA:  Biochemistry     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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