1avd
THREE-DIMENSIONAL STRUCTURE OF THE TETRAGONAL CRYSTAL FORM OF EGG-WHITE AVIDIN IN ITS FUNCTIONAL COMPLEX WITH BIOTIN AT 2.7 ANGSTROMS RESOLUTION
Structural highlights
FunctionAVID_CHICK The biological function of avidin is not known. Forms a strong non-covalent specific complex with biotin (one molecule of biotin per subunit of avidin). 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 PubMedThe three-dimensional structure of hen egg-white avidin, crystallized in a tetragonal crystal form, has been solved at 2.7 A resolution by molecular replacement methods. After refinement the crystallographic R-factor is 16.8%, for the 7255 reflections in the 10.0 to 2.7 A resolution range. The asymmetric unit contains two avidin polypeptide chains (M(r) 2 x 15,600), which build up the functional tetramer through a crystallographic 2-fold axis parallel to the c unit cell direction. The avidin tetramer has almost exact 222 molecular symmetry; the three possible dimers display quite distinct packing interfaces. Each protomer is organized in an eight-stranded antiparallel orthogonal beta-barrel, with extended loop regions. The avidin binding site within each promoter is located in a deep pocket, at the center of the barrel, displaying both hydrophobic and polar residues for recognition of the tightly bound vitamin. Two Trp residues, Trp70 and Trp97, and Phe79 are in close contact with biotin. Moreover, the binding pocket is partly closed in its outer rim by residue Trp110 of a neighboring subunit. Once bound, biotin is almost completely buried in the protein core, with the exception of the valeryl side-chain carboxylate group which is exposed to solvent, hydrogen bonds to residues Ala39, Thr40 and Ser75, and triggers the formation of a network of hydrogen bonded water molecules. Modeling of synthetic biotin analogues allows us to rationalize functional data available for the binding of these compounds, and to analyze them in terms of biotin recognition mechanism. Hen egg-white avidin shows clear structural homology to streptavidin, from Streptomyces avidinii, but significant deviations can be observed in some regions. Three-dimensional structure of the tetragonal crystal form of egg-white avidin in its functional complex with biotin at 2.7 A resolution.,Pugliese L, Coda A, Malcovati M, Bolognesi M J Mol Biol. 1993 Jun 5;231(3):698-710. PMID:8515446[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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