INTRODUCTION

Fatty acid responsive transcription factor (FadR) is a DNA binding protein found in the bacteria escherichia coli. FadR is a dimeric protein that contains two identical sub units containing 239 residues. The major role of FadR is to regulate the transcription of the fatty acid degridation (fad) genes. These genes (fadL, fadD, fadE, fadBA, and fadH) are responsible for fatty acid transport and beta oxidation of fatty acids. Like several other DNA binding proteins found in single celled organisms FadR binds to DNA via a winged helix turn helix (w-HTH) motif in the N terminal of the protein. While FadR is bound to DNA fabA and fabB are activated. These genes produce two carrier proteins which play a specific role in long chain fatty acid syntheses. Therefore, FadR acts as a switch that regulates the synthesis and break down of fatty acids.

When long chain fatty acids become readily available they are then converted into long chain acyl-CoA thioesters. These compounds are able to bind to FadR in the Carboxyl terminal of the protein. When this binding is done FadR undergoes a large confirmational change. This change causes the N terminal to shift, releasing the DNA, allowing for the fad genes to be transcribed. Fatty acid metabolism is then initiated in the organism.

This is the N-terminal where the winged helix turn helix motif is located.

The winged helix turn helix motif is hilighted.

Here the carboxyl terminal of the protein is shown where coenzyme a fatty acids will bind to FadR.