The formation of a native-like structure containing eight conserved hydrophobic residues is rate limiting in two-state protein folding of ACBP

The acyl-coenzyme A-binding proteins (ACBPs) contain 26 highly conserved se quence positions. The majority of these have been mutated in the bovine pro tein, and their influence on the rate of two-state folding and unfolding ha s been measured. The results identify eight sequence positions, out of 24 p robed, that are critical for fast productive folding. The residues are all hydrophobic and located in the interface between the N- and C-terminal heli ces. The results suggest that one specific site dominated by conserved hydr ophobic residues forms the structure of the productive rate-determining fol ding step and that a sequential framework model can describe the protein fo lding reaction.