[Lattice model for globular protein three-dimensional structure].

A discrete, completely determined model is proposed which allows rough evaluation of the polypeptide chain folding in globular proteins with given amino acid sequence. The growth of a self-avording chain begins from the N terminal and is confined by the diamond lattice with prohibition of contacts in the neighbouring junctions of the lattice. The aim function is calculated as the sum of the contributions due to the contacts through the junction as well as the contributions connected with beta sheets. The optimal conformation is found by maximizing the aim function using the cut off method. The model is applied to the trypsin inhibitor and ribonuclease S, provided that the contributions of contacts through the lattice junction are caused by hydrophobic interaction between residues. The results of calculations are shown to depend on the depth of looking over as well as on the parametrization of the aim function. A parametrization is proposed which gives the radia of gyration and matrices of interresidue contacts on agreement with experimental data. The limitations of the lattice model are discussed in connection with the results obtained.