Monomeric bovine beta-lactoglobulin adopts a beta-barrel fold at pH 2.
We have determined a crude structure of the apo form of bovine beta-lactoglobulin, a protein of 162 amino acid residues with a molecular mass of 18 kDa, at a low pH on the basis of data collected using only homonuclear 1H NMR spectroscopy. An ensemble of protein conformations was calculated with the distance-geometry algorithm for NMR applications (DYANA). The monomeric protein at low pH adopts a beta-barrel fold, well-superimposable on the structure determined by X-ray crystallography for the dimer at physiological pH. NMR evidence suggests the presence of disordered loop regions and terminal segments. Structural differences between the monomer at pH 2 and the dimer at pH 7, obtained by X-ray crystallography, are discussed, paying particular attention to surface electrostatic properties, in view of the high charge state of the protein at low pH.
Fogolari
F
F
Istituto Policattedra, Università degli Studi di Verona, Italy.
Ragona
L
L
Zetta
L
L
Romagnoli
S
S
De Kruif
K G
KG
Molinari
H
H
D000465:Algorithms; D000595:Amino Acid Sequence; D000818:Animals; D001059:Apoproteins / Q000737:chemistry; D002417:Cattle; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D007782:Lactoglobulins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D055672:Static Electricity
D001059:Apoproteins; D007782:Lactoglobulins