BIOL 200 Lecture Notes - Lecture 7: Leucine, Histidine, Glutamine
Document Summary
Types of different conformations of dna-binding proteins: zinc-finger motifs -- major class of dna-binding domains. C2h2 zinc finger: zinc + 2 cysteine + 2 histidine = stable, compact finger (alpha helix) that can be inserted into major grooves, usually 3+ units that bind as monomers. C4 zinc finger: usually 2 units that bind as homodimers, each unit bind to inverted repeats, rotation symmetry in conformation, leucine-zipper (example of basic zipper family) Leucine (hydrophobic amino acid) in every 7th position. Hydrophobic interaction between two helices stabilizes dna-binding. Others of the zipper family have different amino acids replacing leucine: basic helix-loop-helix structure. Binding two (or more) unrelated transcription factors that, by themselves, would normally bind to dna w/ weak stability. Usually contains lots of one or two particular amino acids (asp, glu, ser, pro, gln, thr) Acidic activation domains require help of co-activator proteins: phosphorylated creb + cbp, rargamma binds to a ligand (retinoic acid)