  The study of correlated mutations in alignments of homologous proteins proved
to be succesful not only in the prediction of their native conformation, but
also in the developement of a two-body effective potential between pairs of
amino acids. In the present work we extend the effective potential, introducing
a many--body term based on the same theoretical framework, making use of a
principle of maximum entropy. The extended potential performs better than the
two--body one in predicting the energetic effect of 308 mutations in 14
proteins (including membrane proteins). The average value of the parameters of
the many-body term correlates with the degree of hydrophobicity of the
corresponding residues, suggesting that this term partly reflects the effect of
the solvent.
