th  - 1987 - 51st ENC Conference

MKI - POSTERS
NNR STUDIES OF G-LACTALBU~IIN:
MCTERIZATION OF A PARTIALLY UNFOLDED STATE
J. Baum, C.M. Dobson, C. Hanley
Inorganic Chemistry Laboratory
University of Oxford
Oxford, ENGLAND
P.A. Evans
Middlesex Hospital Medical School
London, ENGLAND
To understand the folding mechanism of proteins, it is
important to characterize, at the molecular level, the
structures of states intermediate between the folded and
unfolded conformations. Incompletly folded proteins tend to
have very small IH chemical shift dispersions, therefore
methods have been developed to probe these intermediate states
indirectly via the well-resolved IH spectrum of the native
protein. Guinea-pig ~-lactalbumin provides an especially
favourable system for the investigation of folding due to its
sensitivity to solution conditions; within certain ranges of pH
and temperature there exists a stable partially unfolded
intermediate which we can study by NMR. PH-jump hydrogen
exchange experiments are being developed to assign indirectly,
through the native protein, the labile protons of the unfolded
state, and magnetization transfer experiments are used to
correlate the resonances of the unfolded protein with those of
the native protein. These and other experiments have allowed
us to identify regions of localized structure at the individual
residue level in the unfolded form of ~-lactalbumin.