FOLDING OF CHAINS WITH RANDOM AND EDITED SEQUENCES - SIMILARITIES ANDDIFFERENCES

We have investigated the process of protein folding by Monte-Carlo sim ulation of folding occurring in a simple 3D lattice model of a protein globule. We have found the range of 'optimal' temperatures where the native fold is achieved by the Monte-Carlo process much faster than th at by exhaustive sorting of all the chain folds. The 'optimal' tempera tures are essentially the same for different random and 'edited' seque nces (for the latter, the native fold energy is separated by a conside rable gap from the energies of other tow-energy folds; for random sequ ences, this gap is negligible). At the 'optimal' temperatures, the 'ed ited' chains attain their native fold faster than the random ones. How ever, the essence is that the native folds of 'edited' chains are ther modynamically stable at temperatures optimal for fast folding, while t he native folds of random chains are unstable at the temperatures opti mal for fast folding; also, at low temperatures where the native folds of random chains are stable, folding kinetics is very slow. Consequen tly, stable native folds are formed slowly by random sequences and rap idly by the 'edited' ones.