3EJW

Crystal Structure of the Sinorhizobium meliloti AI-2 receptor, SmLsrB

Summary for 3EJW

• Entry DOI: 10.2210/pdb3ejw/pdb
• Related: 1JX6 1TJY
• Descriptor: SmLsrB, (2R,4S)-2-methyl-2,3,3,4-tetrahydroxytetrahydrofuran (3 entities in total)
• Functional Keywords: periplasmic binding protein, plasmid, signaling protein
• Biological source: Sinorhizobium meliloti (Rhizobium meliloti)
• Total number of polymer chains: 2
• Total formula weight: 68104.37

Authors

Miller, S.T.,McAuley, J.R.,Pereira, C.,Xavier, K.B.,Taga, M.E. (deposition date: 2008-09-18, release date: 2008-12-02, Last modification date: 2024-10-30)

Primary citation

Pereira, C.S.,McAuley, J.R.,Taga, M.E.,Xavier, K.B.,Miller, S.T.
Sinorhizobium meliloti, a bacterium lacking the autoinducer-2 (AI-2) synthase, responds to AI-2 supplied by other bacteria.
Mol.Microbiol., 70:1223-1235, 2008

PubMed Abstract: Many bacterial species respond to the quorum-sensing signal autoinducer-2 (AI-2) by regulating different niche-specific genes. Here, we show that Sinorhizobium meliloti, a plant symbiont lacking the gene for the AI-2 synthase, while not capable of producing AI-2 can nonetheless respond to AI-2 produced by other species. We demonstrate that S. meliloti has a periplasmic binding protein that binds AI-2. The crystal structure of this protein (here named SmlsrB) with its ligand reveals that it binds (2R,4S)-2-methyl-2,3,3,4-tetrahydroxytetrahydrofuran (R-THMF), the identical AI-2 isomer recognized by LsrB of Salmonella typhimurium. The gene encoding SmlsrB is in an operon with orthologues of the lsr genes required for AI-2 internalization in enteric bacteria. Accordingly, S. meliloti internalizes exogenous AI-2, and mutants in this operon are defective in AI-2 internalization. S. meliloti does not gain a metabolic benefit from internalizing AI-2, suggesting that AI-2 functions as a signal in S. meliloti. Furthermore, S. meliloti can completely eliminate the AI-2 secreted by Erwinia carotovora, a plant pathogen shown to use AI-2 to regulate virulence. Our findings suggest that S. meliloti is capable of 'eavesdropping' on the AI-2 signalling of other species and interfering with AI-2-regulated behaviours such as virulence.

PubMed: 18990189
DOI: 10.1111/j.1365-2958.2008.06477.x

Experimental method

X-RAY DIFFRACTION (1.8 Å)