Protein-DNA binding refers to the interaction between proteins and DNA molecules, which is crucial for various biological processes. Proteins, such as transcription factors, recognize specific sequences of DNA to regulate gene expression. This binding can either promote or inhibit the transcription of genes, influencing cellular functions and development. The binding occurs through specific regions on the protein, known as DNA-binding domains, which fit into the grooves of the DNA helix. This interaction is essential for processes like DNA replication, repair, and chromatin remodeling, ensuring that genetic information is accurately maintained and expressed in living organisms.