The Mad1-Sin3B interaction involves a novel helical fold.

Sin3A or Sin3B are components of a corepressor complex that mediates repression by transcription factors such as the helix-loop-helix proteins Mad and Mxi. Members of the Mad/Mxi family of repressors play important roles in the transition between proliferation and differentiation by down-regulating the expression of genes that are activated by ...
the proto-oncogene product Myc. Here, we report the solution structure of the second paired amphipathic helix (PAH) domain (PAH2) of Sin3B in complex with a peptide comprising the N-terminal region of Mad1. This complex exhibits a novel interaction fold for which we propose the name 'wedged helical bundle'. Four alpha-helices of PAH2 form a hydrophobic cleft that accommodates an amphipathic Mad1 alpha-helix. Our data further show that, upon binding Mad1, secondary structure elements of PAH2 are stabilized. The PAH2-Mad1 structure provides the basis for determining the principles of protein interaction and selectivity involving PAH domains.
Mesh Terms:
Amino Acid Sequence, Animals, Binding Sites, Carrier Proteins, Cell Cycle Proteins, Conserved Sequence, Humans, Mice, Models, Molecular, Molecular Sequence Data, Nuclear Magnetic Resonance, Biomolecular, Nuclear Proteins, Phosphoproteins, Protein Binding, Protein Structure, Secondary, Protein Structure, Tertiary, Repressor Proteins, Sequence Alignment, Solutions, Substrate Specificity, Transcription Factors
Nat. Struct. Biol.
Date: Dec. 01, 2000
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