  In order to elucidate the role of the native state topology and the stability
of subdomains in protein folding, we investigate free energy landscape of human
lysozyme, which is composed of two subdomains, by Monte Carlo simulations. A
realistic lattice model with Go-like interaction is used. We take the relative
interaction strength (stability, in other word) of two subdomains as a variable
parameter and study the folding process. A variety of folding process is
observed and we obtained a phase diagram of folding in terms of temperature and
the relative stability. Experimentally-observed diversity in folding process of
c-type lysozimes is thus understood as a consequence of the difference in the
relative stability of subdomains.
