Premium
Protein self‐association in solution: The bovine β ‐lactoglobulin dimer and octamer
Author(s) -
Gottschalk Michael,
Nilsson Hanna,
Roos Helena,
Halle Bertil
Publication year - 2003
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.0305903
Subject(s) - dimer , chemistry , histone octamer , oligomer , monomer , relaxation (psychology) , dispersion (optics) , rotational correlation time , nanosecond , dynamic light scattering , crystallography , molecule , materials science , nucleosome , physics , polymer , nanoparticle , optics , nanotechnology , psychology , social psychology , laser , biochemistry , organic chemistry , gene , histone
We have used proton magnetic relaxation dispersion (MRD) to study the self‐association of bovine β ‐lactoglobulin variant A (BLG‐A) as a function of temperature at pH 4.7 (dimer–octamer equilibrium) and as a function of NaCl concentration at pH 2.5 (monomer–dimer equilibrium). The MRD method identifies coexisting oligomers from their rotational correlation times and determines their relative populations from the associated dispersion amplitudes. From MRD‐derived correlation times and hydrodynamic model calculations, we confirm that BLG‐A dimers associate to octamers below room temperature. The tendency for BLG‐A dimers to assemble into octamers is found to be considerably weaker than in previous light scattering studies in the presence of buffer salt. At pH 2.5, the MRD data are consistent with an essentially complete transition from monomers in the absence of salt to dimers in 1 M NaCl. Because of an interfering relaxation dispersion from nanosecond water exchange, we cannot determine the oligomer populations at intermediate salt concentrations. This nanosecond dispersion may reflect intersite exchange of water molecules trapped inside the large binding cavity of BLG‐A.