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Crystal structures of the LsrR proteins complexed with phospho-AI-2 and its two different analogs reveal distinct mechanisms for ligand recognitionCrystal structures of the LsrR proteins complexed with phospho-AI-2 and its two different analogs reveal distinct mechanisms for ligand recognition
Structural highlights
Function[LSRR_ECOLI] Regulates transcription of many different genes. In the absence of autoinducer 2 (AI-2), represses transcription of the lsrACDBFG operon and its own transcription. In the presence of AI-2, LsrR is inactivated by binding phospho-AI-2, leading to the transcription of the lsr genes.[1] [2] [3] Publication Abstract from PubMedQuorum sensing (QS) is a cell-to-cell communication system responsible for a variety of bacterial phenotypes including virulence and biofilm formation. QS is mediated by small molecules, autoinducers (AIs), including AI-2 that is secreted by both Gram-positive and -negative microbes. LsrR is a key transcriptional regulator that governs the varied downstream processes by perceiving AI-2 signal, but its activation via autoinducer-binding remains poorly understood. Here, we provide detailed regulatory mechanism of LsrR from the crystal structures in complexes with the native signal (phospho-AI-2, D5P) and two quorum quenching antagonists (ribose-5-phosphate, R5P; phospho-isobutyl-AI-2, D8P). Interestingly, the bound D5P and D8P molecules are not the diketone forms but rather hydrated, and the hydrated moiety forms important H-bonds with the carboxylate of D243. The D5P-binding flipped out F124 of the binding pocket, and resulted in the disruption of the dimeric interface-1 by unfolding the alpha7 segment. However, the same movement of F124 by the D8P'-binding did not cause the unfolding of the alpha7 segment. Although the LsrR-binding affinity of R5P (Kd, approximately 1 mM) is much lower than that of D5P and D8P ( approximately 2.0 and approximately 0.5 muM), the alpha-anomeric R5P molecule fits into the binding pocket without any structural perturbation, and thus stabilizes the LsrR tetramer. The binding of D5P, not D8P and R5P, disrupted the tetrameric structure and thus is able to activate LsrR. The detailed structural and mechanistic insights from this study could be useful for facilitating design of new antivirulence and antibiofilm agents based on LsrR. Crystal Structures of the LsrR Proteins Complexed with Phospho-AI-2 and Two Signal-Interrupting Analogues Reveal Distinct Mechanisms for Ligand Recognition.,Ha JH, Eo Y, Grishaev A, Guo M, Smith JA, Sintim HO, Kim EH, Cheong HK, Bentley WE, Ryu KS J Am Chem Soc. 2013 Oct 16;135(41):15526-35. doi: 10.1021/ja407068v. Epub 2013, Oct 1. PMID:24047255[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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