Solution structure and dynamics of bovine β-lactoglobulin A

Using heteronuclear NMR spectroscopy, we studied the solution structure and dynamics of bovine beta-lactoglobulin A at pH 2.0 and 45 degrees C, where the protein exists as a monomeric native state. The monomeric NMR structure, comprising an eight-stranded continuous antiparallel beta-barrel and one major alpha-helix, is similar to the X-ray dimeric structure obtained at pH 6.2, including beta(I)-strand that forms the dimer interface and loop EF that serves as a lid of the interior hydrophobic hole. {H-1}-N-15 NOE revealed that beta(F), beta(G), and beta(H) strands buried under the major alpha-helix are rigid on a pico- to nanosecond time scale and also emphasized rapid fluctuations of loops and the N- and C-terminal regions.