3mbt

Structure of monomeric Blc from E. coli

spinqualitylabelsall models 3mbt, resolution 2.60Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 3mbt 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. Related: 1qwd, 2aco Gene: b4149, blc, JW4110, yjeL (Escherichia coli) Resources: FirstGlance, OCA, RCSB, PDBsum Function [BLC_ECOLI] Involved in the storage or transport of lipids necessary for membrane maintenance under stressful conditions. Displays a binding preference for lysophospholipids. Publication Abstract from PubMed The first bacterial member of the lipocalin protein family, Blc, was identified in Escherichia coli as an outer membrane lipoprotein that is expressed under conditions of environmental stress. Previous crystallographic studies in space group P222 with two molecules per asymmetric unit, supported by static light-scattering experiments in solution, indicated that Blc may form a functional homodimer with lysophospholipid binding activity. Here, a new crystal structure of recombinant Blc in space group I422 with one molecule in the asymmetric unit is described. The crystal packing differs considerably from that observed previously, which was determined using an N-terminally extended version of Blc dubbed `Blc-X'. In particular, the characteristic large interface region that was previously described as being responsible for stable dimer formation is absent in the I422 crystal structure. Thus, the dimerization behaviour of Blc-X was most likely to be caused by the additional N-terminal peptide segment resulting from the cloning strategy employed. In contrast, we used a native-like N-terminus for Blc with just the lipid-anchored first Cys residue replaced by Ala. The fully monomeric status of this recombinant version of Blc in solution was confirmed by size-exclusion chromatography as well as analytical ultracentrifugation. Consequently, these data shed new light on the previously postulated lipid-binding mechanism and biological role of Blc. Beyond this, our findings illustrate that cloning artefacts, which frequently result from recombinant protein production for structural studies, must be considered with special caution when interpreting oligomerization and/or conformational effects. Structural and biochemical analyses reveal a monomeric state of the bacterial lipocalin Blc.,Schiefner A, Chatwell L, Breustedt DA, Skerra A Acta Crystallogr D Biol Crystallogr. 2010 Dec;66(Pt 12):1308-15. Epub 2010, Nov 16. PMID:21123871 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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