In the present paper a new lattice model of proteins is proposed which is based on non-local cooperative interactions. In this model the energy of a conformation of a polymer is equal to the sum of energies of conformations of fragments of the polymer chain of length five.
It is shown that this quinary lattice model is able to describe at a qualitative level secondary structures of proteins: for this model all conformations with minimal energy are combinations of lattice models of alpha-helix and beta-strand. Moreover for lattice polymers of length not longer that 38 monomers we can describe all conformations with minimal energy.