Sandbox Reserved 779: Difference between revisions
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Binding of variety of small hydrophobic molecules | Binding of variety of small hydrophobic molecules | ||
<Structure load='1gx8' size='150' frame='true' align='left' caption='Fig. 2 β-lactoglobulin complexed with Retinol, trigonal lattice Z_1GX8' scene='Insert optional scene name here' /> | |||
Retinol and Palmitate Binding | Retinol and Palmitate Binding | ||
β-lactoglobulin (β-Lg) is a lipocalin, like plasma retinol-binding protein, so that ligand association was expected to make use of the central cavity in the protein.<ref>PMID:12054801</ref> | β-lactoglobulin (β-Lg) is a lipocalin, like plasma retinol-binding protein, so that ligand association was expected to make use of the central cavity in the protein.<ref>PMID:12054801</ref> | ||
A cocrystallized β-Lg with palmitic acid, and the refined structure (R = 0.204, R free = 0.240 for 6,888 reflections to 2.5-Å resolution) reveals that the ligand binds in the central cavity in a manner similar to the binding of retinol to the related lipocalin, serum retinol-binding protein.<ref>PMID:9867826</ref> It is probably also involved in the transport of that molecule.<ref>PMID:15259212</ref>. | A cocrystallized β-Lg with palmitic acid (Fig. 2), and the refined structure (R = 0.204, R free = 0.240 for 6,888 reflections to 2.5-Å resolution) reveals that the ligand binds in the central cavity in a manner similar to the binding of retinol (Fig. 3)to the related lipocalin, serum retinol-binding protein.<ref>PMID:9867826</ref> It is probably also involved in the transport of that molecule.<ref>PMID:15259212</ref>. | ||
<Structure load='1b0o' size='150' frame='true' align='right' caption='Fig. 3 β-lactoglobulin complexed with Palmitate, lattice Z_1B0O' scene='Insert optional scene name here' /> | |||
== Structure of β-Lactoglobulin == | == Structure of β-Lactoglobulin == | ||
β-Lactoglobulin consists of 162 amino acid residues (18 kDa), containing two disulfide bonds (Cys 66–Cys 160 and Cys 106–Cys 119) and a free thiol (Cys 121). Structures of βLG have been reported by several groups with X-ray crystallography [19–21] and solution NMR [29,40,41].<ref>PMID:19362581</ref> | β-Lactoglobulin consists of 162 amino acid residues (18 kDa), containing two disulfide bonds (Cys 66–Cys 160 and Cys 106–Cys 119) and a free thiol (Cys 121). Structures of βLG have been reported by several groups with X-ray crystallography [19–21] and solution NMR [29,40,41].<ref>PMID:19362581</ref> | ||
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The loops that connect the β-strands at the closed end of the calyx, BC, DE, and FG,are generally quite short, whereas those at the open end, AB, CD, EF,and GH, are significantly longer and more flexible [19]. In the calyx,there is a large central cavity which is surrounded by hydrophobic residues and is accessible to solvent. This cavity provides the principal ligand-binding site. βLG contains two tryptophan residues, Trp 19 on the A strand and Trp 61 on the C strand. The former is buried in the hydrophobic core whereas the latter is exposed to the solvent in the native structure, making them useful probes for monitoring site-specific conformational changes.<ref>PMID:19362581</ref> | The loops that connect the β-strands at the closed end of the calyx, BC, DE, and FG,are generally quite short, whereas those at the open end, AB, CD, EF,and GH, are significantly longer and more flexible [19]. In the calyx,there is a large central cavity which is surrounded by hydrophobic residues and is accessible to solvent. This cavity provides the principal ligand-binding site. βLG contains two tryptophan residues, Trp 19 on the A strand and Trp 61 on the C strand. The former is buried in the hydrophobic core whereas the latter is exposed to the solvent in the native structure, making them useful probes for monitoring site-specific conformational changes.<ref>PMID:19362581</ref> | ||
<Structure load='2q2m' size='150' frame='true' align='right' caption='Fig.4 The Native form of β-lactoglobulin_Monomer_2Q2M' scene='Insert optional scene name here' /> | |||
In addition, studies on the monomer–dimer equilibrium [30,32,42,43] and the reactivity of the thiol group of Cys121 which deeply buried between the α-helix and H strand [44–48] revealed other important properties of β-LG.<ref>PMID:19362581</ref> the stability of the structure also depend so heavily upon the external loop around residue 64 or the β strand with the free thiol.<ref>PMID:9115437</ref> | In addition, studies on the monomer–dimer equilibrium [30,32,42,43] and the reactivity of the thiol group of Cys121 which deeply buried between the α-helix and H strand [44–48] revealed other important properties of β-LG.<ref>PMID:19362581</ref> the stability of the structure also depend so heavily upon the external loop around residue 64 or the β strand with the free thiol.<ref>PMID:9115437</ref> | ||
At physiological conditions, bovine b-lactoglobulin forms a dimer (Fig. 1), with each monomer consisting of 162 amino acid residues and characterized by a molecular mass of 18,350. Below pH 3, the dimer dissociates into | At physiological conditions, bovine b-lactoglobulin forms a dimer (Fig. 1), with each monomer consisting of 162 amino acid residues and characterized by a molecular mass of 18,350. Below pH 3, the dimer dissociates into monomers (Fig. 4) which preserve their native conformation.<ref>PMID:11734004</ref> | ||
Genetically, b-lactoglobulin may exist as one of several variants, among which the variants A and B are the most abundant. The A and B variants of the protein differ from each other by amino acid residues at positions Asp64 (Gly64 in variant B) and Val118 (Ala118 in variant B). These differences in primary structure render the two variants slightly different with respect to isoelectric point, solubility, self-association properties, as well as pressure and temperature stability.<ref>PMID:11734004</ref> | Genetically, b-lactoglobulin may exist as one of several variants, among which the variants A and B are the most abundant. The A and B variants of the protein differ from each other by amino acid residues at positions Asp64 (Gly64 in variant B) and Val118 (Ala118 in variant B). These differences in primary structure render the two variants slightly different with respect to isoelectric point, solubility, self-association properties, as well as pressure and temperature stability.<ref>PMID:11734004</ref> | ||
