1pnz

Crystal structure of ferric citrate transporter FecA in the unliganded form

spinqualitylabelsall models 1pnz, resolution 2.50Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1pnz is a 1 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.5Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function FECA_ECOLI FecA is the outer membrane receptor protein in the Fe(3+) dicitrate transport system. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Escherichia coli possesses a TonB-dependent transport system, which exploits the iron-binding capacity of citrate and its natural abundance. Here, we describe three structures of the outer membrane ferric citrate transporter FecA: unliganded and complexed with iron-free or diferric dicitrate. We show the structural mechanism for discrimination between the iron-free and ferric siderophore: the binding of diferric dicitrate, but not iron-free dicitrate alone, causes major conformational rearrangements in the transporter. The structure of FecA bound with iron-free dicitrate represents the first structure of a TonB-dependent transporter bound with an iron-free siderophore. Binding of diferric dicitrate to FecA results in changes in the orientation of the two citrate ions relative to each other and in their interactions with FecA, compared to the binding of iron-free dicitrate. The changes in ligand binding are accompanied by conformational changes in three areas of FecA: two extracellular loops, one plug domain loop and the periplasmic TonB-box motif. The positional and conformational changes in the siderophore and transporter initiate two independent events: ferric citrate transport into the periplasm and transcription induction of the fecABCDE transport genes. From these data, we propose a two-step ligand recognition event: FecA binds iron-free dicitrate in the non-productive state or first step, followed by siderophore displacement to form the transport-competent, diferric dicitrate-bound state in the second step. Structural evidence for iron-free citrate and ferric citrate binding to the TonB-dependent outer membrane transporter FecA.,Yue WW, Grizot S, Buchanan SK J Mol Biol. 2003 Sep 12;332(2):353-68. PMID:12948487 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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