Final answer:
Leucine zippers are motifs in proteins that facilitate dimerization and DNA binding, playing a significant role in gene regulation, as seen in plant defense mechanisms.
Step-by-step explanation:
The structure of a leucine zipper in regulatory DNA-binding proteins (RDPs) involves a motif that facilitates the dimerization of two protein monomers. Each monomer's zipper region contains leucine residues at every seventh position, contributing to a coiled-coil formation. This allows it to interact with DNA through a basic region that binds to specific sequences, promoting gene transcription. An example of this interaction is seen through bZIP (basic leucine zipper) proteins in plant defense, such as the regulation of PR (pathogen-related) genes by the TGA protein in response to a pathogen attack. LSD1, with a zinc finger domain, also interacts with AtbZIP10, demonstrating a form of regulatory interaction in plants facing oxidative stress.