1dv9
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STRUCTURAL CHANGES ACCOMPANYING PH-INDUCED DISSOCIATION OF THE B-LACTOGLOBULIN DIMER
OverviewOverview
We have used NMR spectroscopy to determine the three-dimensional (3D), structure, and to characterize the backbone dynamics, of a recombinant, version of bovine beta-lactoglobulin (variant A) at pH 2. 6, where the, protein is a monomer. The structure of this low-pH form of, beta-lactoglobulin is very similar to that of a subunit within the dimer, at pH 6.2. The root-mean-square deviation from the pH 6.2 (crystal), structure, calculated for backbone atoms of residues 6-160, is, approximately 1.3 A. Differences arise from the orientation, with respect, to the calyx, of the A-B and C-D loops, and of the flanking three-turn, alpha-helix. The hydrophobic cavity within the calyx is retained at low, pH. The E-F loop (residues 85-90), which moves to occlude the opening of, the cavity over the pH range 7.2-6.2, is in the "closed" position at pH, 2.6, and the side chain of Glu89 is buried. We also carried out, measurements of (15)N T(1)s and T(2)s and (1)H-(15)N heteronuclear NOEs at, pH 2.6 and 37 degrees C. Although the residues of the E-F loop (residues, 86-89) have the highest crystallographic B-factors, the conformation of, this loop is reasonably well defined by the NMR data, and its backbone is, not especially mobile on the pico- to nanosecond time scale. Several, residues (Ser21, Lys60, Ala67, Leu87, and Glu112) exhibit large ratios of, T(1) to T(2), consistent with conformational exchange on a micro- to, millisecond time scale. The positions of these residues in the 3D, structure of beta-lactoglobulin are consistent with a role in modulating, access to the hydrophobic cavity.
About this StructureAbout this Structure
1DV9 is a Single protein structure of sequence from Bos taurus. Full crystallographic information is available from OCA.
ReferenceReference
Structural changes accompanying pH-induced dissociation of the beta-lactoglobulin dimer., Uhrinova S, Smith MH, Jameson GB, Uhrin D, Sawyer L, Barlow PN, Biochemistry. 2000 Apr 4;39(13):3565-74. PMID:10736155
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