DIFFUSION-COLLISION MODEL FOR THE FOLDING KINETICS OF THE LAMBDA-REPRESSOR OPERATOR-BINDING DOMAIN

The operator-binding domain of the .lambda.-repressor contains 5 .alpha.-helices and an extended N-terminal arm in the crystal structure determined by Pabo and Lewis. The 4 helices form a box enclosing a hydrophobic core, with the 5th helix interacting with the equivalent helix in a dimer. With a small number of well-defined secondary structure elements (microdomains), the repressor is well suited for an analysis of its folding pathways and kinetics by use of the diffusion-collision model. In this paper, the basic elements of the model appropriate to a several microdomain protein were formulated and applied to a set of folding pathways consistent with the crystal structure of the operator-binding domain. The overall kinetics and the time-dependence of intermediate states were determined as a function of the microdomain stability parameter.