期刊
PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS
卷 80, 期 3, 页码 713-721出版社
WILEY
DOI: 10.1002/prot.23228
关键词
Dps; electrophoretic mobility shift assay; DNA binding; stoichiometry; mini-ferritin
资金
- National Science Foundation [MCB-0744240, MCB-1051610]
- Div Of Biological Infrastructure
- Direct For Biological Sciences [1051610] Funding Source: National Science Foundation
DNA protection during starvation (Dps) proteins, dodecameric assemblies of four-helix bundle subunits, contribute to protection against reactive oxygen species. Deinococcus radiodurans, which is characterized by resistance to DNA damaging agents, encodes two Dps homologs, of which Dps-1 binds DNA with high affinity. DNA binding requires N-terminal extensions preceding the four-helix bundle core. Composed of six Dps-1 dimers, each capable of DNA binding by N-terminal extensions interacting in consecutive DNA major grooves, dodecameric Dps-1 would be predicted to feature six DNA binding sites. Using electrophoretic mobility shift assays and intrinsic tryptophan fluorescence, we show that dodecameric Dps-1 binds 22-bp DNA with a stoichiometry of 1:6, consistent with the existence of six DNA binding sites. The stoichiometry of Dps-1 binding to 26-bp DNA is 1:4, suggesting that two Dps-1 dodecamers can simultaneously occupy opposite faces of this DNA. Mutagenesis of an arginine (Arg132) on the surface of Dps-1 leads to a reduction in DNA binding. Altogether, our data suggest that duplex DNA lies along the dimer interface, interacting with Arg132 and the N-terminal a-helices, and they extend the hexagonal packing model for DpsDNA assemblies by specifying the basis for occupancy of available DNA binding sites. Proteins 2011; (c) 2012 Wiley Periodicals, Inc.
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