User:Wayne Decatur/Gal 4: Difference between revisions

<Structure load='Insert PDB code or filename here' size='550' frame='true' align='right' caption='The N-terminal amino acids of Gal4p bound to DNA ([[1d66]])' scene='70/701975/1d66_firstglance/1' />

The protein <scene name='70/701975/1d66_firstglance/1'>binds as a dimer to a symmetrical 17-base-pair sequence</scene>. Specifically, the consensus Gal4p-binding site is a 17-mer of sequence conforming to the motif below.<br>

The DNA binding domain <scene name='70/701975/1d66_firstglance_zn_binding/1'>uses six Cys residues to coordinate the binding of two ions of zinc (Zn(II))</scene>. In the crystal structure [[1d66]], the zinc ions are represented by other members of the same group on the periodic table, the heavier cadmium ions. The Zn-binding motif lets the structure accomplish more with fewer amino acids, the metals lending an "economy of structure", arranging two small helices to recognize a specific DNA site.

The third large helix of each dimer subunit interacts with the other <scene name='70/701975/1d66_firstglance_slab/1'>by arranging hydrophobic residues in the contact region</scene>. Note the abundance of gray residues in the central stem protruding from a site roughly the center of the DNA binding site. The dimer interface is more fully explored in a later publication with an expanded structure, see [[3coq]].