title: Structural basis for phosphorylated autoinducer-2 modulation of the oligomerization state of the global transcription regulator LsrR from Escherichia coli.
abstract: Quorum-sensing systems are widely used by bacteria to control behavior in response to fluctuations in cell density. Several small diffusible molecules called autoinducers act as signaling molecules in quorum-sensing processes through interplay with sensors. Autoinducers modulate vital physiological functions such as nutrient acquisition, gene transcription, and virulence factor production. In Escherichia coli, LsrR serves as a global transcription regulator that responds to autoinducer-2 to regulate the expression of a variety of genes, including the lsr operon and the lsrR gene. Here, we report the crystal structure of full-length LsrR from E. coli, which has an N-terminal DNA-binding domain and a C-terminal ligand-binding domain connected by a β-strand. Although only two molecules are found in one asymmetric unit, two neighboring dimers pack to form a tetramer that is consistent with the oligomerization state of LsrR in solution. Mutagenesis experiments and gel shift assays indicated that Gln-33 and Tyr-26 might be involved in interactions between LsrR and DNA. The LsrR-binding site for phosphorylated autoinducer-2 was predicted by structural comparisons of LsrR with CggR and SorC. Cross-linking, size exclusion chromatography, and gel shift assays determined that phosphorylated autoinducer-2 triggered the disassembly of the LsrR tetramer into dimers and reduced the DNA binding ability of LsrR. Our findings reveal a mechanism for the change in the oligomerization state of LsrR in the presence of phosphorylated autoinducer-2. Based on these observations, we propose that phosphorylated autoinducer-2 triggers the disassembly of the LsrR tetramer to activate the transcription of its target genes.
authors.affiliation: Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Minhao
authors.initials: M
authors.lastname: Wu
authors.forename: Yue
authors.initials: Y
authors.lastname: Tao
authors.forename: Xiaotian
authors.initials: X
authors.lastname: Liu
authors.forename: Jianye
authors.initials: J
authors.lastname: Zang
mesh_terms: D018360:Crystallography, X-Ray; D004269:DNA, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006714:Homoserine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007783:Lactones / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D011485:Protein Binding; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic / Q000502:physiology*
chemical_list: D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D007783:Lactones; C504601:LsrR protein, E coli; C091088:N-octanoylhomoserine lactone; D012097:Repressor Proteins; D006714:Homoserine
keywords: Crystal Structure; DNA-binding Protein; LsrR; Molecular Docking; Quorum Sensing; Transcription Regulation