CONFORMATION OF GROEL-BOUND ALPHA-LACTALBUMIN PROBED BY MASS-SPECTROMETRY

The conformation of a three-disulphide derivative of bovine alpha-lact albumin bound to the molecular chaperone GroEL has been investigated b y monitoring directly its hydrogen exchange kinetics using electrospra y ionization mass spectrometry. The bound protein is weakly protected from exchange to an extent closely similar to that of an uncomplexed m olten globule state of the three-disulphide protein. Binding to GroEL in this system appears to involve relatively disordered partly folded states resembling intermediates formed in the very early stages of kin etic folding of many proteins in vitro.