Multiple oligomeric states regulate the DNA binding of helix-loop-helix peptides. |
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Authors: | R Fairman R K Beran-Steed S J Anthony-Cahill J D Lear W F Stafford rd W F DeGrado P A Benfield and S L Brenner |
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Institution: | R Fairman, R K Beran-Steed, S J Anthony-Cahill, J D Lear, W F Stafford, 3rd, W F DeGrado, P A Benfield, and S L Brenner |
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Abstract: | To study the protein-protein interactions that allow Id, a negative regulator of cell differentiation, to inhibit the DNA-binding activities of MyoD and E47, we have synthesized peptides corresponding to the helix-loop-helix domains of MyoD, E47, and Id. We show that Id preferentially inhibits the sequence-specific DNA-binding activity of MyoD, a muscle-specific protein, as compared to E47, a more ubiquitous protein. The Id helix-loop-helix domain itself forms stable tetramers, and its inhibitory activity arises from the formation of a heterotetrameric structure with MyoD. The formation of this higher order complex provides a general mechanism by which inhibitory proteins can generate sufficient interaction free energy to overcome the large DNA-binding free energy of dimeric DNA-binding proteins. |
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