2aco
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Xray structure of Blc dimer in complex with vaccenic acid
OverviewOverview
Lipocalins, a widespread multifunctional family of small proteins, (15-25kDa) have been first described in eukaryotes and more recently in, Gram-negative bacteria. Bacterial lipocalins belonging to class I are, outer membrane lipoproteins, among which Blc from E. coli is the better, studied. Blc is expressed under conditions of starvation and high, osmolarity, conditions known to exert stress on the cell envelope. The, structure of Blc that we have previously solved (V. Campanacci, D., Nurizzo, S. Spinelli, C. Valencia, M. Tegoni, C. Cambillau, FEBS Lett. 562, (2004) 183-188.) suggested its possible role in binding fatty acids or, phospholipids. Both physiological and structural data on Blc, therefore, point to a role in storage or transport of lipids necessary for membrane, maintenance. In order to further document this hypothesis for Blc, function, we have performed binding studies using fluorescence quenching, experiments. Our results indicate that dimeric Blc binds fatty acids and, phospholipids in a micromolar K(d) range. The crystal structure of Blc, with vaccenic acid, an unsaturated C18 fatty acid, reveals that the, binding site spans across the Blc dimer, opposite to its membrane anchored, face. An exposed unfilled pocket seemingly suited to bind a polar group, attached to the fatty acid prompted us to investigate lyso-phospholipids, which were found to bind in a nanomolar K(d) range. We discuss these, findings in terms of a potential role for Blc in the metabolism of, lysophospholipids generated in the bacterial outer membrane.
About this StructureAbout this Structure
2ACO is a Single protein structure of sequence from Escherichia coli with VCA as ligand. Full crystallographic information is available from OCA.
ReferenceReference
The membrane bound bacterial lipocalin Blc is a functional dimer with binding preference for lysophospholipids., Campanacci V, Bishop RE, Blangy S, Tegoni M, Cambillau C, FEBS Lett. 2006 Sep 4;580(20):4877-83. Epub 2006 Aug 10. PMID:16920109
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