As sequential dimerization did not occur with the ETS domain of Ets-1, a close structural homolog of PU.1, 2:1 complex formation may represent an alternative autoinhibitory mechanism in the ETS family at the protein-DNA level. The site-specifically bound PU.1 dimer resisted competition from nonspecific DNA and showed affinities similar to other functionally significant PU.1 interactions. Hydroxyl radical DNA footprinting indicated that the site-specifically bound PU.1 dimers occupied an extended DNA interface downstream from the 5′-GGAA-3′ core consensus relative to its 1:1 counterpart, thus explaining the apparent site size requirement for sequential dimerization. NMR spectroscopy revealed a marked loss of signal intensity in the 2:1 complex, and mutational analysis implicated the distal surface away from the bound DNA as the dimerization interface. Whereas 10 bp of DNA was sufficient to support PU.1 binding as a monomer, additional flanking bases were required to invoke sequential dimerization of the bound protein. Following our previous observation by titration calorimetry that the ETS member PU.1 dimerizes sequentially at a single sequence-specific DNA-binding site to form a 2:1 complex, we have carried out an extensive spectroscopic and biochemical characterization of site-specific PU.1 ETS complexes. The eponymous DNA-binding domain of ETS ( E26 transformation- specific) transcription factors binds a single sequence-specific site as a monomer over a single helical turn. The ETS 93-98 Toyota Supra is one of the largest intercoolers available and with core sizes ranging from 4.0 thick up to 6.0 we have everything from 400hp to 1600hp Features: 30x12x4 Overall Dimensions (tank to tank) 24x12x4 Bar & Plate Core.
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