  In this work we have studied, with the help of a simple on-lattice model, the
distribution pattern of sites sensitive to point mutations ('hot' sites) in
protein-like chains. It has been found that this pattern depends on the
regularity of the matrix that rules the interaction between different kinds of
residues. If the interaction matrix is dominated by the hydrophobic effect
(Miyazawa Jernigan like matrix), this distribution is very simple - all the
'hot' sites can be found at the positions with maximum number of closest
nearest neighbors (bulk).
  If random or nonlinear corrections are added to such an interaction matrix
the distribution pattern changes. The rising of collective effects allows the
'hot' sites to be found in places with smaller number of nearest neighbors
(surface) while the general trend of the 'hot' sites to fall into a bulk part
of a conformation still holds.
