A major driving force for water-soluble protein folding is the hydrophobic
effect, but membrane proteins cannot make use of this stabilizing contribution
in the apolar core of the bilayer. It has been proposed that membrane proteins
compensate by packing more efficiently. We therefore investigated packing
contributions experimentally by observing the energetic and structural
consequences of cavity creating mutations in the core of a membrane protein. We
observed little difference in the packing energetics of water and membrane
soluble proteins. Our results imply that other mechanisms are employed to
stabilize the structure of membrane proteins.
