Preface: Quorum Sensing in the bacterial world

Quorum sensing (QS) is a system in which stimulus and response are regulated according to population density. Studies on QS have been most extensive on proteobacteria although QS is not exclusive to prokaryote (Pratt et al (2002) wrote about how ants utilise QS to guide other ants to a new nest). QS enables bacteria lacking the mammalian senses of vision/smell/touch to sense their surrounding population and react accordingly to maintain survival in competitive environment. One of the very vivid description of QS is the bioluminescence in Vibrio fischeri, which is responsible for the 'Klingon cloaking device' in squids (see Youtube video below). Our 'Quorum Sensing' page contains a brief account of the component and mechanism of quorum sensing.

QS operates by regulating the synthesis of a QS signal, Acyl Homoserine Lactone (AHL), and its cognate receptor, which doubles as a transcription factor that affects other gene transcriptional activities. In this blog we attempt to scrutinize a specific QS signal receptor, QscR, by looking into its structural characteristics, and comparing QscR with other homologous receptors such as LasR, TraR, CviR and SdiA to analyse what they may have in common or how they differ. We have also included a list of techniques which are employed in the structural study of QscR under 'Methodology'. References have been cited throughout and included together with acknowledgement at the last page. On top of each page there is a brief statement which summarizes the content. 

PyMOL derived crystal structure showing QscR dimer (Chain A: magenta, Chain B: blue).
Ligands (3OC12-HSL) in ligand binding domain of each chain are shown as spheres.