Authors: Zhihong Cheng1,5, Ya-Wen He1,5, Siew Choo Lim1,4,5, Rohini Qamra1,5, Martin A. Walsh2 Lian-Hui Zhang3 and Haiwei Song1,3,4.
1 - Institute of Molecular and Cell Biology, 61 Biopolis Drive, Proteos, Singapore 138673.
2 - 2MRC France, CRG BM14, ESRF, B.P.220, F-38043, Grenoble CEDEX, France.
3 - Department of Biological Sciences, National University of Singapore, 14 Science Drive, Singapore 117543.
4 - School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551.
5 - These authors contributed equally.
Published in Structure, 2010 Sept 8, 18(9): 199-209.
The diffusible signal factor (DSF)-dependent quorum sensing (QS) system adopts a novel protein-protein interaction mechanism to auto-regulate the production of signal DSF. Here we present the crystal structures of DSF synthase RpfF and its complex with the REC domain of sensor protein RpfC. RpfF is structurally similarity to the members of the crotonase superfamily and contains an N-terminal α/β spiral core domain and a C-terminal α-helical region. Further structural and mutational analysis identified two catalytic glutamate residues, which is the conserved feature of the enoyl-CoA hydratases/dehydratases. A putative substrate-binding pocket was unveiled and the key roles of the residues implicated in substrate binding were verified by mutational analysis. The binding of the REC domain may lock RpfF in an inactive conformation by blocking the entrance of substrate binding pocket, thereby negatively regulating DSF production. These findings provide a structural model for the RpfC-RpfF interaction-mediated novel QS autoinduction mechanism.