[18] Molecular applications of fusions to leucine zippers

The use of chimeric proteins to study protein function dates back as far as the use of illegitimate recombination events among lambdoid phage to generate interspecies variants containing different amounts of polypeptide derived from each parent. Recombinant deoxyribonucleic acid (DNA) methods made the use of fusion proteins more easily generalizable and allowed fundamentally important insights to be derived for many biological systems. For example, understanding of transcriptional activation was fundamentally altered by the experiments of Brent and Ptashne, who showed that targeting of an activation domain to a particular chromosomal location through a fused bacterial LexA DNA-binding protein was sufficient to activate transcription. There are now many ways to use fused motifs to hold proteins together. This chapter briefly discusses the use of natural and mutant leucine zippers as molecular damps.